louis pasteur meat experiment

How the Scientific Method Works

Share Content on Facebook
Share Content on LinkedIn
Share Content on Flipboard
Share Content on Reddit
Share Content via Email

Pasteur's Experiment

The steps of Pasteur's experiment are outlined below:

First, Pasteur prepared a nutrient broth similar to the broth one would use in soup.

Next, he placed equal amounts of the broth into two long-necked flasks. He left one flask with a straight neck. The other he bent to form an "S" shape.

Then he boiled the broth in each flask to kill any living matter in the liquid. The sterile broths were then left to sit, at room temperature and exposed to the air, in their open-mouthed flasks.

After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed.

He concluded that germs in the air were able to fall unobstructed down the straight-necked flask and contaminate the broth. The other flask, however, trapped germs in its curved neck, preventing them from reaching the broth, which never changed color or became cloudy.

If spontaneous generation had been a real phenomenon, Pasteur argued, the broth in the curved-neck flask would have eventually become reinfected because the germs would have spontaneously generated. But the curved-neck flask never became infected, indicating that the germs could only come from other germs.

Pasteur's experiment has all of the hallmarks of modern scientific inquiry. It begins with a hypothesis and it tests that hypothesis using a carefully controlled experiment. This same process — based on the same logical sequence of steps — has been employed by scientists for nearly 150 years. Over time, these steps have evolved into an idealized methodology that we now know as the scientific method. After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed.

Let's look more closely at these steps.

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

3.1 Spontaneous Generation

Learning objectives.

By the end of this section, you will be able to:

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

Clinical Focus

Barbara is a 19-year-old college student living in the dormitory. In January, she came down with a sore throat, headache, mild fever, chills, and a violent but unproductive (i.e., no mucus) cough. To treat these symptoms, Barbara began taking an over-the-counter cold medication, which did not seem to work. In fact, over the next few days, while some of Barbara’s symptoms began to resolve, her cough and fever persisted, and she felt very tired and weak.

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

Humans have been asking for millennia: Where does new life come from? Religion, philosophy, and science have all wrestled with this question. One of the oldest explanations was the theory of spontaneous generation, which can be traced back to the ancient Greeks and was widely accepted through the Middle Ages.

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“spirit” or “breath”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. 1

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 3.2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. 2 He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. 3 As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 3.3 ).

Check Your Understanding

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur , a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 3.4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan-neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” 4 To Pasteur’s credit, it never has.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
1 K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf
2 E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196.
3 R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206.
4 R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142.

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Access for free at https://openstax.org/books/microbiology/pages/1-introduction

Authors: Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster
Publisher/website: OpenStax
Book title: Microbiology
Publication date: Nov 1, 2016
Location: Houston, Texas
Book URL: https://openstax.org/books/microbiology/pages/1-introduction
Section URL: https://openstax.org/books/microbiology/pages/3-1-spontaneous-generation

© Jul 18, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.

History & Society
Science & Tech
Biographies
Animals & Nature
Geography & Travel
Arts & Culture
Games & Quizzes
On This Day
One Good Fact
New Articles
Lifestyles & Social Issues
Philosophy & Religion
Politics, Law & Government
World History
Health & Medicine
Browse Biographies
Birds, Reptiles & Other Vertebrates
Bugs, Mollusks & Other Invertebrates
Environment
Fossils & Geologic Time
Entertainment & Pop Culture
Sports & Recreation
Visual Arts
Demystified
Image Galleries
Infographics
Top Questions
Britannica Kids
Saving Earth
Space Next 50
Student Center

What did Louis Pasteur discover?
What did Louis Pasteur invent?
What was Louis Pasteur’s family like?

close up of 3d microscopic blue bacteria

spontaneous generation

Our editors will review what you’ve submitted and determine whether to revise the article.

Biology LibreTexts - Spontaneous Generation
Open Oregon Educational Resources - Spontaneous Generation
Academia - Spontaneous Generation

spontaneous generation , the hypothetical process by which living organisms develop from nonliving matter; also, the archaic theory that utilized this process to explain the origin of life . According to that theory, pieces of cheese and bread wrapped in rags and left in a dark corner, for example, were thus thought to produce mice , because after several weeks there were mice in the rags. Many believed in spontaneous generation because it explained such occurrences as the appearance of maggots on decaying meat.

By the 18th century it had become obvious that higher organisms could not be produced by nonliving material. The origin of microorganisms such as bacteria , however, was not fully determined until Louis Pasteur proved in the 19th century that microorganisms reproduce. See also biopoiesis .

2.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont, a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 2 .2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

Francesco Redi’s experimental setup consisted of an open container, a container sealed with a cork top, and a container covered in mesh that let in air but not flies. Maggots only appeared on the meat in the open container. However, maggots were also found on the gauze of the gauze-covered container.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. [3] As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 2 .3 ).

(a) Francesco Redi, who demonstrated that maggots were the offspring of flies, not products of spontaneous generation. (b) John Needham, who argued that microbes arose spontaneously in broth from a “life force.” (c) Lazzaro Spallanzani, whose experiments with broth aimed to disprove those of Needham.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur, a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 2 .4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan- neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” [4] To Pasteur’s credit, it never has.

(a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur ’s experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur’s experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination. In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became contaminated.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur, trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

Allied Health Microbiology Copyright © 2019 by Open Stax and Linda Bruslind is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Share This Book

Lessons and Courses on Microbiology

SPONTANEOUS GENERATION (ABIOGENESIS)

Spontaneous generation (abiogenesis) is the mistaken hypothesis that living organisms are capable of being generated from non-living things. Mankind for many centuries (even till the time of Aristotle in 4 th century BC) previously believed that non-living things such as meat and even decaying organic matter can generate living things (e.g. maggot). The belief that life can emanate from non-life was widely accepted as at the time even by scientists who could have experimented on it to either disprove or accept the theory.

Nevertheless several scientists (including John Needham , Francesco Redi , John Tyndall and Louis Pasteur ) as at the time abiogenesis was accepted were curious on how the concept of abiogenesis was true and relevant. This led this notable scientist’s to conduct series of experiments which led to the final disapproval of the theory of spontaneous generation.

Spontaneous generation (though an obsolete biological theory) sparked a lot of controversies for many years in the world; and scientists, religious leaders and especially philosophers had different views as to how life originated. A wider part of the society as at the time believed that life could originate from nothing especially from non-living things or some kind of vital forces that were present in decomposing organic matter.

The concept of spontaneous generation was very appealing to some scientists and even philosophers as at the time who believed strongly that life originated from non-life, but religious leaders fought against it because they believed that life originated from a supernatural being. In the subsequent pages, we shall discover that spontaneous generation does not occur, and that life does not emanate from non-life but from pre-existing life as exemplified by the notable works of Louis Pasteur amongst others.

How did life originated? The increase in knowledge, human’s quest for understanding life and the development of the scientific method gave man a better perspective of his environment and how the organisms in it (inclusive of microorganisms) directly or indirectly affect him. Previously, people believed so many things even when they did not conduct experiment to know if what they observed in their immediate natural environment is true or not. The theory of spontaneous generation held-sway for a long period of time before it was challenged and disproven through the experimental works of some notable scientists like Louis Pasteur. It is noteworthy that the scientists who attempted to disprove abiogenesis carried out their experiments or testing based on the scientific method.

Scientific method is the general approach that involves series of systematic steps or modus operandi used by scientists (including microbiologists) to conduct research. This methodical approach enables scientists (anywhere in the world) to conduct make scientific inquiries and arrive at conclusive answers to their observations or questions; and scientific method is a universally accepted approach of conducting research by scientists. The basic steps involved in the scientific method (which may vary depending on the experimentation) are elaborated in Figure 1.

Before it was disproved, people believed that life originated from non-living matter, a biological phenomenon known as spontaneous generation. Biogenesis is an alternative hypothesis to spontaneous generation; and it postulates that living organisms originated from pre-existing living things. Those who supported the claims of spontaneous generation (i.e. abiogenesis) believed that living organisms arise from non-living things or decomposing organic matter; and this hypothesis was invoke even till the late 19 th century before it was disproven by series of experiments conducted by notable scientists.

Francesco Redi (1626-1697) , an Italian Physicianwas the first to attack the theory of spontaneous generation, and this happened in 1668. At a time when it was widely believed that maggots arose from decaying meat, Redi carried out his experiment by filling a series of jars with decaying meat in order to disprove this belief. Some of the jars was left completely open to the air ( the test ); others were completely sealed while the remaining jars was covered with fine clothe or gauze (which prevented insects from entering). The flasks or jars that were completely sealed and covered with gauze served as the controls.

Francesco Redi believed that flies deposited eggs on the decaying meat, and this resulted to the development of maggots on the meat. After some days, it was discovered that maggots appeared only in the open jars in which the flies could easily reach and lay their eggs. Maggots did not appear in the jars that where completely sealed or covered with gauze. The laying of eggs on the decaying meat led to the development of maggots on the meat, and this was enough for Redi to disprove the theory of spontaneous generation. Francesco Redi challenged the theory of spontaneous generation by showing in his jar-decaying meat experiment that the maggot that appeared on the decaying meat (in the opened jar) came from the eggs of the fly deposited on the meat, and that the meat did not produce them. Despite Redi’s significant experiment (which gave impetus to the origin of life), the theory of spontaneous generation or abiogenesis remained strong and this continued for many centuries.

John Needham (1713-1781) used the boiling technique to determine whether or not boiling killed microorganisms. Needham supported the theory of spontaneous generation with his mutton or chicken broth boiling flask technique. He boiled mutton broth and put it in a flask which was tightly sealed after the broth was introduced in it. It was believed that boiling kills microorganisms. Needham allowed the flask for a long period of time, and discovered later that microorganisms developed in the broth even after boiling. Though his experiment supported abiogenesis; the fight to disprove spontaneous generation continued.

Lazzaro Spallanzani (1729-1799) , an Italian cleric boiled nutrient solutions in flask, and he showed in his experiment (which was a modification of Needham’s) that flask containing broth when sealed and boiled had no microbial growth. He drew out air from the flask before boiling in order to create a partial vacuum in the medium. Lazzaro was not convinced with Needham’s experiment because he contemplated that microorganisms could have entered the broth after it was boiled and before it was sealed. He showed in his significant work that air carried germs or microorganisms to the broth, and that air could support the growth of the organisms in the broth. However, Lazzaro’s experiment was still not accepted by supporters of spontaneous generation who believed that abiogenesis could not occur in the absence of air.

The theory of spontaneous generation was later put to rest and totally disproven by the significant experiments of Louis Pasteur (1822-1895) in 1859 and John Tyndall ( 1820-1893 ), an English physicist who extended Pasteur’s work by working on heat-resistant bacteria . A French chemist and microbiologist, Pasteur used the swan-necked flask experiment ( Figure 2 ) to disprove the theory of spontaneous generation. Louis Pasteur improved on the works of Needham and Spallanzani by boiling meat broth in bent-flasks which was opened to the air. Pasteur suggested that microorganisms in the air (which could contaminate the sterile broth) would be trapped on the sides of the bent flasks before they could finally reach the broth; and that if sterile broth had no prior contact with microorganisms, the broth would still remain sterile or free from microbes.

Louis Pasteur boiled meat broth in a flask and heated the neck of the flask in a flame until it became bent or curved (i.e. swan-necked). Though air could easily enter the flask, microorganisms in the air would be trapped in the neck of the bent flask. This was Pasteur’s idea of disproving the theory of spontaneous generation. The curved or bent flasks containing the broth were boiled to kill any form of microorganisms in it; and the flask was observed for a period of time for any possible microbial growth. But if the neck of the bent-flask was broken, dust particles or air-borne microbes would enter the flask and the broth will become polluted, and this will support the growth of germs.

Pasteur’s swan-necked experiment showed that the broth remained sterile for months because air-borne microbes were trapped in the bent-neck of the flask. Louis Pasteur then concluded that life only arises from life, and this is known as biogenesis. Though Louis Pasteur’s work laid the theory of spontaneous generation to rest; his notable experiment also showed that microbes are ubiquitous i.e. they are everywhere (even in the air).

The theory of spontaneous generation was wildly acceptable to many as at the time it was invoke, but the experiments of Louis Pasteur and that of John Tyndall helped in laying it to rest once and for all. John Tyndall ( 1820-1893 ) gave impetus to the experiment of Louis Pasteur by showing in 1877 that dust particles indeed harboured microbes, and that the absence of it could cause the broth to remain sterile.

Tyndall went a step further to show the existence of heat-resistant forms of bacteria known as endospores , which are not easily killed by boiling. It is possible that the bacterial growth that was observed in Needham’s experiment after boiling was endopores (i.e. heat-resistant forms of bacteria). The observance of bacterial growth after boiling chicken broth made Needham to propose in 1745 that spontaneous generation did occur because microbes grew after the process. However, Pasteur and Tyndall’s experiment put a final stop to the theory of spontaneous generation and they convincingly showed that abiogenesis did not actually occur.

Barrett J.T (1998). Microbiology and Immunology Concepts. Philadelphia, PA: Lippincott-Raven Publishers. USA.

Beck R.W (2000). A chronology of microbiology in historical context. Washington, D.C.: ASM Press.

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23 rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Chung K.T, Stevens Jr., S.E and Ferris D.H (1995). A chronology of events and pioneers of microbiology. SIM News , 45(1):3–13.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Salyers A.A and Whitt D.D (2001). Microbiology: diversity, disease, and the environment. Fitzgerald Science Press Inc. Maryland, USA.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

Summers W.C (2000). History of microbiology. In Encyclopedia of microbiology, vol. 2, J. Lederberg, editor, 677–97. San Diego: Academic Press.

Talaro, Kathleen P (2005). Foundations in Microbiology. 5 th edition. McGraw-Hill Companies Inc., New York, USA.

Wainwright M (2003). An Alternative View of the Early History of Microbiology. Advances in applied microbiology. Advances in Applied Microbiology, 52:333–355.

Willey J.M, Sherwood L.M and Woolverton C.J (2008). Harley and Klein’s Microbiology. 7 th ed. McGraw-Hill Higher Education, USA.

Introduction to (Medical) Bacteriology

Microbial Growth

Louis Pasteur, Spontaneous Generation, and Germ Theory

“For I have kept from them, and am still keeping from them, that one thing which is above the power of man to make; I have kept from them the germs that float in the air, I have kept them from life.” - Louis Pasteur

“For I have kept from them, and am still keeping from them, that one thing which is above the power of man to make; I have kept from them the germs that float in the air, I have kept them from life.” – Louis Pasteur (1)

May 19, 1861 is a date that probably doesn’t ring a bell or cause any light bulbs to go off in terms of huge scientific events. In the United States, people weren’t thinking too much about science. The Civil War was only five weeks old, and Union and Confederate gunships were trying, to no avail, to capture the Chesapeake Bay (2) .

In England, Charles Darwin’s On the Origin of Species had already been in circulation for a year and a half, leaving scientific revolution and controversy in its wake. (3) Elsewhere in Europe, Gregor Mendel still tended the pea plants that became the basis of what we now know as “classical” genetics after he presented his work to the scientific world in 1865 (4) . And in Paris, a chemist named Louis Pasteur presented an experiment in front of his colleagues at the Paris Society for Chemistry that would turn the scientific world and much of what we believed on its head (5) .

Prior to Pasteur’s experiment, a belief called “spontaneous generation” was a prevalent scientific method to explain how life came to be. This belief outlined that life can essentially arise from anything, even out of thin air. So if a piece of meat spoiled, the cause of the spoilage simply materialized from the air!

What Pasteur did was put the belief of spontaneous generation to rest with a simple, yet brilliant experiment. Pasteur boiled some nutrient broth inside a flask with a long, twisted neck. The flask, while still open to the air, did not allow any microbes to enter the main area of the flask where the sterile broth was. Any bacteria in the air couldn’t pass through the long neck of the flask to get to the broth inside. No bacteria meant no contamination, and the broth stayed sterile for one whole year! Pasteur then broke the neck of the flask and exposed the broth to the microbe-filled air, which contaminated the broth in short order.

Life Comes From Life

What is the ultimate impact of Pasteur’s experiment? He didn’t win the Nobel Prize for it (the first Nobel Prizes were awarded in 1901, and Pasteur died in 1895) (1, 6) .

But there came a shift in attitude regarding how life came to be. The idea that “life comes from life” is now one of the major tenets of biology. Its significance is right up there with evolution and the cell theory (7) .

Even more significantly, Pasteur’s experiment had an even greater impact on medicine. In the years following Pasteur’s experiment, Pasteur and one of his contemporaries (and eventually, his bitter rival) Robert Koch began studying various diseases closely and concluded that specific microbes have the ability to cause specific diseases (1, 8, 9) .

This is the germ theory of disease. This theory led to the successful identification and treatment of many microbial diseases (1) , saving millions of lives and contributing to the development of what we know today as modern medicine.

All because of a chemist and his funny-looking flask.

References:

Talaro, Kathleen Park, and Barry Chess. Foundations in Microbiology , ninth edition. New York: McGraw-Hill (2015).
Battle Summary: Sewell’s Point, VA . CWSCA Battle Summaries: The American Battlefield Preservation Program (ABPP) . Retrieved from https://www.nps.gov/abpp/Battles/va001.htm
Darwin, Charles. On the Origin of Species by Means of Natural Selection . London: John Murray (1859). Retrieved from https://www.gutenberg.org/files/1228/1228-h/1228-h.htm
Mendel, Gregor.Versuche über Pflanzen-Hybriden. Verh. Naturforsch. Ver. Brünn 4: 3–47 (1866) (Article in German). Retrieved from http://www.biodiversitylibrary.org/item/124139#page/133/mode/1up
Pasteur, Louis. Sur les corpuscles organisés qui existent dans l’atmosphère: Examen de la doctrine des générations spontanées. Leçon Professée a la Société Chimique de Paris, le 19 Mai 1861 (Article in French).
Nobel Prize Facts. Retrieved from http://www.nobelprize.org/nobel_prizes/facts/
Simon, Eric J., Dickey, Jean L., Hogan, Kelly A, and Jane B. Reece. Campbell Essential Biology, sixth edition. New York: Pearson Higher Education (2016).
Smith, Kendall. Louis Pasteur, the father of immunology? Frontiers in Immunology 3(68), 1-10 (April 2012).
Blevins, Steve M., and Bronze, Michael S. Robert Koch and the ‘golden age’ of bacteriology. International Journal of Infectious Diseases 14: e744–e751 (2010).

About the Author

Craig Fenn is in his fourth year of teaching for the American Public University in the School of Science, Technology, Engineering and Math, with a primary teaching assignment of SCIN 130 (Introduction to Biology with Lab). His primary employer is at Reading Area Community College, where he serves as the course lead for Principles of Biology and Microbiology as well as the chair of the Campus Life Committee. He is a native of Connecticut currently living outside of Lancaster, PA.

Are near-death experiences just hallucinations?
How to Become an Amateur Scientist (and Why You Should)
What is the future of television?
Shinya Yamanaka: the godfather of induced pluripotent stem cells

Recent news

Possible First-Ever Sighting of a Great White Shark Birth Stuns Researchers

Scientists Revive 1,000-Year-Old Seed, Potentially Resurrecting Mysterious Biblical Tree

Meet the Sea Robin: A Fish That Walks and Tastes the Seafloor With Its Legs

Editorial Policy
Privacy Policy and Terms of Use
How we review products

Science News
Environment
Natural Sciences
Matter and Energy
Quantum Mechanics
Thermodynamics
Periodic Table
Applied Chemistry
Physical Chemistry
Biochemistry
Microbiology
Plants and Fungi
Planet Earth
Earth Dynamics
Rocks and Minerals
Invertebrates
Conservation
Animal facts
Climate change
Weather and atmosphere
Diseases and Conditions
Mind and Brain
Food and Nutrition
Anthropology
Archaeology
The Solar System
Asteroids, meteors & comets
Astrophysics
Exoplanets & Alien Life
Spaceflight and Exploration
Computer Science & IT
Engineering
Sustainability
Renewable Energy
Green Living
Editorial policy
Privacy Policy

Site search
Through the Microscope
Why Microbes Matter
Remember me
Log in page
Create new account
Recover lost username
Recover lost password
Contact the Author
Contact the Webmaster

Latest News

1-6 spontaneous generation was an attractive theory to many people, but was ultimately disproven..

( 62995 Reads)

Learning Objectives

After reading this section, students will be able to...

Explain why people believed in the concept of spontaneous generation, the creation of life from organic matter.
Describe the experiment by Francesco Redi disproved spontaneous generation that disproved spontaneous generation for macroorganisms.
Explain how did John Needham's experiment re-ignited the debate about spontaneous generation for microorganisms.
Describe the swan-neck flask experiment of Louis Pasteur and why this ended the debate about spontaneous generation.

Spontaneous generation hypothesizes that some vital force contained in or given to organic matter can create living organisms from inanimate objects. Spontaneous generation was a widely held belief throughout the middle ages and into the latter half of the 19 th century. Some people still believe in it today. The idea was attractive because it meshed nicely with the prevailing religious views of how God created the universe. There was a strong bias to legitimize the idea because this vital force was considered a strong proof of God's presence in the world. Proponents offered many recipes and experiments in proof. To create mice, mix dirty underwear and wheat grain in a bucket and leave it open outside. In 21 days or less, you would have mice. The real cause may seem obvious from a modern perspective, but to the supporters of this idea, the mice spontaneously arose from the wheat kernels.

Another often-used example was the generation of maggots from meat left in the open. Francesco Redi revealed the failing here in 1668 with a classic experiment. Redi suspected that flies landing on the meat laid eggs that eventually grew into maggots . To test this idea, he devised the experiment shown in Figure 1.11. Here he used three pieces of meat. Redi placed one piece of meat under a piece of paper. The flies could not lay eggs onto the meat, and no maggots developed. The second piece was left in the open air, resulting in maggots. In the final test, Redi overlayed the third piece of meat with cheesecloth. The flies could lay the eggs into the cheesecloth, and when he removed this, no maggots developed. However, if Redi placed the cheesecloth containing the eggs on a fresh piece of meat, maggots developed, showing it was the eggs that "caused" maggots and not spontaneous generation. Redi ended the debate about spontaneous generation for large organisms. However, spontaneous generation was so seductive a concept that even Redi believed it was possible in other circumstances.

Figure 1.11. The Redi experiment. . Using several pieces of meat, paper and cheesecloth, Francesco Redi produced compelling evidence against the theory of spontaneous generation. One of the strong points of this experiment was its simplicity, which allowed others to easily reproduce it for themselves. See the text for details of the experiment.

The concept and the debate were revived in 1745 by the experiments of John Needham. It was known at the time that heat was lethal to living organisms. Needham theorized that if he took chicken broth and heated it, all living things in it would die. After heating some broth, he let a flask cool and sit at a constant temperature. The development of a thick turbid solution of microorganisms in the flask was strong proof to Needham of the existence of spontaneous generation. Lazzaro Spallanzani later repeated the experiments of Needham, but removed air from the flask, suspecting that the air was providing a source of contamination. No growth occurred in Spallanzani's flasks, and he took this as evidence that Needham was wrong. Proponents of spontaneous generation discounted the experiment by asserting that the vital force needed air to work properly.

It was not until almost 100 years later that the great French chemist Louis Pasteur, pictured in Figure 1.12, put the debate to rest. He first showed that the air is full of microorganisms by passing air through gun cotton filters. The filter trapped tiny particles floating in the air. By dissolving the cotton with an ether/alcohol mixture, the particles were released and then settled to the bottom of the liquid. Inspection of this material revealed numerous microbes that resembled the types of bacteria often found in putrefying media. Pasteur realized that if these bacteria were present in the air, they would likely land on and contaminate any exposed material.

Figure 1.12. Louis Pasteur . The French microbiologist Louis Pasteur. Drawing by Tammi Henke

Pasteur then entered a contest sponsored by The French Academy of Sciences to disprove the theory of spontaneous generation. Similar to Spallanzani's experiments, Pasteur's experiment, pictured in Figure 1.13, used heat to kill the microbes but left the end of the flask open to the air. In a simple but brilliant modification, he heated the neck of the flask to melting and drew it out into a long S-shaped curve, preventing the dust particles and their load of microbes from ever reaching the flask. After prolonged incubation, the flasks remained free of life and ended the debate for most scientists.

Figure 1.13. The swan neck flask experiment . Pasteur filled a flask with medium, heated it to kill all life, and then drew out the neck of the flask into a long S shape. This prevented microorganisms in the air from easily entering the flask, yet allowed some air interchange. If the swan neck was broken, microbes readily entered the flask and grew

A final footnote on the topic was added when John Tyndall show ed the existence of heat-resistant spores in many materials. Boiling does not kill these spores, and their presence in chicken broth, as well as many other materials, explains the results of Needham's experiments.

While this debate may seem silly from a modern perspective, remember that the scientists of the time had little knowledge of microorganisms. Koch would not isolate microbes until 1881. The proponents of spontaneous generation were neither sloppy experimenters nor stupid. They did careful experiments and interpreted them with their own biases. Detractors of the theory of spontaneous generation were just as guilty of bias but in the opposite direction. It is somewhat surprising that Pasteur and Spallanzoni did not get growth in their cultures since the sterilization conditions they used would often not kill endospores . Luck certainly played a role. It is important to keep in mind that the discipline of science is performed by humans with all the fallibility and bias inherent in the species. Only the self-correcting nature of the practice reduces the impact of these biases on generally held theories. Spontaneous generation was a severe test of scientific experimentation because it was such a seductive and widely held belief. Yet, even spontaneous generation was overthrown when the weight of careful experimentation argued against it. Table 1.3 lists important events in the spontaneous generation debate.

Table 1.3 Events in spontaneous generation

Year	Event
1668	Francesco Redi attacks spontaneous generation and disproves it for large organisms
1745	John Needham adds chick broth to a flask and boils it, lets it cool and waits. Microbes grow and he proposes it as an example of spontaneous generation.
1768	Lazzaro Spallanzani repeats Needham's experiment, but removes all the air from the flask. No growth occurs.
1859	Louis Pasteur's swan-neck flasks show that spontaneous generation does not occur.
1870	Thomas H. Huxley gives his "Biogenesis and Abiogenesis" lecture. The speech offered powerful support for Pasteur's claim to have experimentally disproved spontaneous generation.
1877	John Tyndall publishes his method for fractional sterilization, showing the existence of heat-resistant bacterial spores.

Key Takeaways

For many centuries many people believed in the concept of spontaneous generation, the creation of life from organic matter.
Francesco Redi disproved spontaneous generation for large organisms by showing that maggots arose from meat only when flies laid eggs in the meat.
Spontaneous generation for small organisms again gained favor when John Needham showed that if a broth was boiled (presumed to kill all life) and then allowed to sit in the open air, it became cloudy.
Louis Pasteur ended the debate with his famous swan-neck flask experiment, which allowed air to contact the broth. Microbes present in the dust were not able to navigate the tortuous bends in the neck of the flask.

Is Spontaneous Generation Real?

Cell Biology
Weather & Climate
B.A., Biology, Emory University
A.S., Nursing, Chattahoochee Technical College

For several centuries it was believed that living organisms could spontaneously come from nonliving matter. This idea, known as spontaneous generation, is now known to be false. Proponents of at least some aspects of spontaneous generation included well-respected philosophers and scientists such as Aristotle, Rene Descartes, William Harvey, and Isaac Newton . Spontaneous generation was a popular notion due to the fact that it seemed to be consistent with observations that a number of animal organisms would apparently arise from nonliving sources. Spontaneous generation was disproved through the performance of several significant scientific experiments.

Key Takeaways

Spontaneous generation is the idea that living organisms can spontaneously come from nonliving matter.
Over the years great minds like Aristotle and Isaac Newton were proponents of some aspects of spontaneous generation which have all been shown to be false.
Francesco Redi did an experiment with meat and maggots and concluded that maggots do not arise spontaneously from rotting meat.
The Needham and the Spallanzani experiments were additional experiments that were conducted to help disprove spontaneous generation.
The Pasteur experiment was the most famous experiment conducted that disproved spontaneous generation that was accepted by the majority of the scientific community. Pasteur demonstrated that bacteria appearing in broth are not the result of spontaneous generation.

Do Animals Spontaneously Generate?

Prior to the mid-19th century, it was commonly believed that the origin of certain animals was from nonliving sources. Lice were thought to come from dirt or sweat. Worms, salamanders, and frogs were thought to be birthed from the mud. Maggots were derived from rotting meat, aphids and beetles supposedly sprang from wheat, and mice were generated from soiled clothing mixed with wheat grains. While these theories seem quite ludicrous, at the time they were thought to be reasonable explanations for how certain bugs and other animals seemed to appear from no other living matter.

Spontaneous Generation Debate

While a popular theory throughout history, spontaneous generation was not without its critics. Several scientists set out to refute this theory through scientific experimentation. At the same time, other scientists tried to find evidence in support of spontaneous generation. This debate would last for centuries.

Redi Experiment

In 1668, the Italian scientist and physician Francesco Redi set out to disprove the hypothesis that maggots were spontaneously generated from rotting meat. He contended that the maggots were the result of flies laying eggs on exposed meat. In his experiment, Redi placed meat in several jars. Some jars were left uncovered, some were covered with gauze, and some were sealed with a lid. Over time, the meat in the uncovered jars and the jars covered with gauze became infested with maggots. However, the meat in the sealed jars did not have maggots. Since only the meat that was accessible to flies had maggots, Redi concluded that maggots do not spontaneously arise from meat.

Needham Experiment

In 1745, English biologist and priest John Needham set out to demonstrate that microbes, such as bacteria , were the result of spontaneous generation. Thanks to the invention of the microscope in the 1600s and increased improvements to its usage, scientists were able to view microscopic organisms such as fungi , bacteria, and protists. In his experiment, Needham heated chicken broth in a flask in order to kill any living organisms within the broth. He allowed the broth to cool and placed it in a sealed flask. Needham also placed unheated broth in another container. Over time, both the heated broth and unheated broth contained microbes. Needham was convinced that his experiment had proven spontaneous generation in microbes.

Spallanzani Experiment

In 1765, Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. He contended that microbes are capable of moving through the air. Spallanzani believed that microbes appeared in Needham's experiment because the broth had been exposed to air after boiling but before the flask had been sealed. Spallanzani devised an experiment where he placed the broth in a flask, sealed the flask, and removed the air from the flask before boiling. The results of his experiment showed that no microbes appeared in the broth as long as it remained in its sealed condition. While it appeared that the results of this experiment had dealt a devastating blow to the idea of spontaneous generation in microbes, Needham argued that it was the removal of air from the flask that made spontaneous generation impossible.

Pasteur Experiment

In 1861, Louis Pasteur presented evidence that would virtually put an end to the debate. He designed an experiment similar to Spallanzani's, however, Pasteur's experiment implemented a way to filter out microorganisms. Pasteur used a flask with a long, curved tube called a swan-necked flask. This flask allowed air to have access to the heated broth while trapping dust containing bacterial spores in the curved neck of the tube. The results of this experiment were that no microbes grew in the broth. When Pasteur tilted the flask on its side allowing the broth access to the curved neck of the tube and then set the flask upright again, the broth became contaminated and bacteria reproduced in the broth. Bacteria also appeared in the broth if the flask was broken near the neck allowing the broth to be exposed to non-filtered air. This experiment demonstrated that bacteria appearing in broth are not the result of spontaneous generation. The majority of the scientific community considered this conclusive evidence against spontaneous generation and proof that living organisms only arise from living organisms.

Microscope, Through the. “Spontaneous Generation Was an Attractive Theory to Many People, but Was Ultimately Disproven.” Through the Microscope Main News , www.microbiologytext.com/5th_ed/book/displayarticle/aid/27.
Life and Contributions of Robert Koch, Founder of Modern Bacteriology
All About Photosynthetic Organisms
Angiosperms
Phases of the Bacterial Growth Curve
Biology of Invertebrate Chordates
What Is an Action Potential?
Animal Viruses
Slowest Animals on the Planet
5 Tricks Plants Use to Lure Pollinators
Chromosome Structure and Function
7 Scary Diseases Caused by Bacteria
The Photosynthesis Formula: Turning Sunlight into Energy
Parts of a Flowering Plant
What Is Phylogeny?
7 Fascinating Facts About Fungi
What Is a Trophic Level?

Microbe Notes

Experiments in support and against Spontaneous Generation

Spontaneous generation is an obsolete theory which states that living organisms can originate from inanimate objects.
The theory believed that dust created fleas, maggots arose from rotting meat, and bread or wheat left in a dark corner produced mice among others.
Although the idea that living things originate from the non-living may seem ridiculous today, the theory of spontaneous generation was hotly debated for hundreds of years.
During this time, many experiments were conducted to both prove and disprove the theory.

Table of Contents

Interesting Science Videos

Experiments in Support of Spontaneous Generation

The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms, and was taken as scientific fact for two millennia.

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter.
Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”).
As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water.

John Needham

The English naturalist John Turberville Needham was in support of the theory.
Needham found that large numbers of organisms subsequently developed in prepared infusions of many different substances that had been exposed to intense heat in sealed tubes for 30 minutes.
Assuming that such heat treatment must have killed any previous organisms, Needham explained the presence of the new population on the grounds of spontaneous generation.
By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding.
Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared.
Jan Baptista van Helmont , a seventeenth century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks.

Experiments against Spontaneous Generation

Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani, spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

Francesco Redi

The Italian physician and poet Francesco Redi was one of the first to question the spontaneous origin of living things.
Having observed the development of maggots and flies on decaying meat, Redi in 1668 devised a number of experiments, all pointing to the same conclusion: if flies are excluded from rotten meat, maggots do not develop. On meat exposed to air, however, eggs laid by flies develop into maggots.
He tested the spontaneous creation of maggots by placing fresh meat in each of two different jars.
One jar was left open; the other was covered with a cloth. Days later, the open jar contained maggots, whereas the covered jar contained no maggots.
He did note that maggots were found on the exterior surface of the cloth that covered the jar. Redi successfully demonstrated that the maggots came from fly eggs.

Lazzaro Spallanzani

The experiments of Needham appeared irrefutable until the Italian physiologist Lazzaro Spallanzani repeated them and obtained conflicting results.
He published his findings around 1775, claiming that Needham had not heated his tubes long enough, nor had he sealed them in a satisfactory manner.
Although Spallanzani’s results should have been convincing, Needham had the support of the influential French naturalist Buffon; hence, the matter of spontaneous generation remained unresolved.

Louis Pasteur

Louis Pasteur ‘s 1859 experiment is widely seen as having settled the question of spontaneous generation.
He boiled a meat broth in a flask that had a long neck that curved downward, like that of a goose or swan.
The idea was that the bend in the neck prevented falling particles from reaching the broth, while still allowing the free flow of air.
The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded.
This work was so conclusive; that biology codified the “Law of Biogenesis,” which states that life only comes from previously existing life.

John Tyndall

Support for Pasteur’s findings came in 1876 from the English physicist John Tyndall, who devised an apparatus to demonstrate that air had the ability to carry particulate matter.
Because such matter in air reflects light when the air is illuminated under special conditions, Tyndall’s apparatus could be used to indicate when air was pure.
Tyndall found that no organisms were produced when pure air was introduced into media capable of supporting the growth of microorganisms.
It was those results, together with Pasteur’s findings, that put an end to the doctrine of spontaneous generation.
Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
https://study.com/academy/lesson/spontaneous-generation-definition-theory-examples.html
https://www.britannica.com/science/biology#ref498783
https://www.infoplease.com/science/biology/origin-life-spontaneous-generation
https://www.allaboutscience.org/what-is-spontaneous-generation-faq.htm
https://courses.lumenlearning.com/microbiology/chapter/spontaneous-generation/

About Author

Sagar Aryal

The middle years 1862-1877

Louis Pasteur’s work raised a new set of research questions, such as " Where do fermentation agents come from ? " and " Do they originate from germs similar to themselves or do they appear spontaneously as explained by the spontaneous generation theory ? "

Spontaneous generation - the big debate

At the time the spontaneous generation theory was widely accepted in scientific circles. Louis Pasteur decided to approach the issue via his experimental method.

This required the use of swan-necked flasks. Water in the flask was brought to the boil for a few minutes until the steam escaped from the open end of the flask. It was then left to cool. While cooling, the air entering the flask deposited dust and germs on the first bend. Although in contact with outside air the liquid remained unaltered because germs could not get through.

Louis Pasteur showed that microbes were omnipresent - in water, in air, on objects, on the skin – and that some were responsible for diseases.

After some memorable struggles against his opponents, notably the famous biologist and fierce defender of the spontaneous generation theory, Félix Pouchet, in his 1862 paper Louis Pasteur was able to claim that :

airborne dust contained microorganisms which develop and multiply.
even the most putrescible liquids remained unadulterated if kept away from air (and hence these microorganisms) after heating.

He recommended ways of preventing and fighting these germs, and thus the habits essential for personal and social hygiene . This notably included the use of aseptic procedure s, i.e. the various measures to be taken to prevent invasion of live tissue or inert environments by exogenous microorganisms or viruses. He advocated the importance of sterilization of linen and dressings, passing instruments through a flame and clean hands . These recommendations led to the widespread advent of modern surgery.

So how does fermentation work ?

But Louis Pasteur still had ferments in mind. He pondered on fermentation and how ferments work. While studying butyric fermentation he discovered a new class of living organisms capable of living without air.

He used the term " anaerobic " to describe ferments able to live without air and " aerobic " for microorganisms requiring the presence of free oxygen to grow.

He came to the conclusion that fermentation is the consequence of life without air.

He applied his microbiological method to industry and agriculture to eradicate ancient diseases affecting crops and products.

To the rescue of industry and agriculture

He studied the formation of vinegar and the conversion of alcohol into acetic acid by Mycoderma aceti, which fixes oxygen from the air onto the alcohol. He showed vinegar makers how to produce vinegar of consistent quality by avoiding contamination by harmful mycoderma.

Wine diseases

Wine was France flagship industry and a difficult business in many respects. Winemakers had difficulty guaranteeing the quality of their production which was affected by diseases of no known cause or cure. The crisis was nothing new but risked damaging exports and above all trade agreements in place with England. Emperor Napoleon III called on Louis Pasteur to seek a solution. First he showed that each wine disease was due to a particular ferment. He developed a protocol to fight the diseases, heating the wine to between 55°C and 60°C, a temperature at which it does not deteriorate and its bouquet is preserved. This method is now known worldwide as pasteurization .

Just like wine, beer is infected by microorganisms transmitted by airborne dust. Louis Pasteur taught brewers to preserve the wort from the impurities and to heat the beer to 55° to prevent disease.

Silkworm diseases

In 1865, disease hit the silk industry. In France, this posed a threat to the economy of an entire region and the disease spread further afield to other silk-producing countries such as Italy, Austria and Asia Minor. Louis Pasteur discovered that silkworms were affected by two diseases - silkworm nosema disease and flacherie.

Under the microscope, Louis Pasteur noticed that the worms with nosema disease developed shiny corpuscles, and showed that the disease was both hereditary and contagious. He developed the cellular egg production method to enable the preservation of healthy silkworm eggs. He isolated the female moths to allow them to lay their eggs separately. After laying, he ground the female moths and examined them under the microscope. If the shiny corpuscles were observed he destroyed the eggs, otherwise he kept them for breeding. As for flacherie, he introduced the "specific terrain" concept, i.e. the physiological condition of the infected host favoring outbreak of the disease. A few hygiene rules, good ventilation and quarantine of the suspect batches sufficed to prevent contamination. These simple processes saved the silk industry from doom. But the research was of considerable value, paving the way for the study of contagious diseases. For the first time problems of heredity and contagion were scientifically proven and prophylaxis rules were established. The time had now come for Louis Pasteur to address human diseases.

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

3. The Cell

3.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

CLINICAL FOCUS: Part 1

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain moulded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

An open container with meat has flies and the formation of maggots in meat. A cork-sealed container of meat has no flies and no formation of maggots in meat. A gauze covered container of meat has flies and maggots on the surface of the gauze but no maggots in the meat.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

a) drawing of Francesco Redi. B) drawing of John Needham c) drawing of Lazzaro Spallanzani.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

a) Photo of Louis Pasteur b) Photo of Pasteur’s swan-necked flask, c) A drawing of Pasteur’s experiment that disproved the theory of spontaneous generation.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

Key Takeaways

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
Experimentation by Francesco Redi in the 17th century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation.
Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

Multiple Choice

Fill in the blank, short answer.

Explain in your own words Pasteur’s swan-neck flask experiment.
Explain why the experiments of Needham and Spallanzani yielded in different results even though they used similar methodologies.

Critical Thinking

What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?

Media Attributions

OSC_Microbio_03_01_Rediexpt
https://link.springer.com/content/pdf/10.1007%2Fs10739-017-9494-7.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

Share This Book

Spontaneous Generation Theory

Table of Contents

Aristotle’s Work

Early experiments, franceso redi, pier antonio micheli, john needham, lazzaro spallanzani, disproving the theory, louis pasteur, john tyndall, frequently asked questions.

Spontaneous generation theory is an archaic scientific theory which stated that living organisms could arise from nonliving matter and that such a process was regular in nature. It also explained the origin of life from the nonliving subjects. According to that theory, a piece of bread and cheese wrapped and left in a corner could give rise to mice in a few weeks, or maggots could rise from dead flesh.

The hypothesis was designed by Aristotle on the basis of previous work of natural philosophers and the theory held its place for two millenniums. Francesco Redi and Lazzaro Spallanzani then challenged this theory in the 17th and 18th centuries, but it was still not discredited. It was not until the work of Louis Pasteur and John Tyndall in the 19th century that this theory was finally disproved.

The theory lines up with the theory of origin of life, which states the process of abiogenesis. Abiogenesis is the natural process of creation of simple organic compounds from nonliving matter. The term equivocal generation, also called heterogenesis, describes the theory of spontaneous generation. According to equivocal generation, one life arises from another unrelated life form.

According to Aristotle, every living being is made up of a compound of matter and form. In his sexual theory of reproduction, he stated that male’s semen was efficient cause that passed down characteristics to female matter (menstrual blood), and gave rise to its offspring. He believed that the male semen and female matter were refinements that were produced by bodies as a result of their proportions of heat, ingested food and were a byproduct of the elements earth and water. Yet, he believed that creatures arose from spontaneous generation and not sexual reproduction.

Analogous to his sexual reproduction theory, he said that non living matter just like seminal fluid had ‘pneuma’ or ‘vital heat’ that endowed the subtances with vital properties. He came to the conclusion that whether a life form arose from sexual reproduction or spontaneous generation, they were a result of interaction between vital heat and elemental matter.

Franceso Redi was an Italian naturalist who challenged the ancient belief of spontaneous generation of maggots on decaying meat in 1668. He believed that maggots could be prevented if flies were not allowed direct contact with the meat. He designed an experiment where he put pieces of meat in six different containers. He covered two of them with gauze, two tightly sealed with corks and left the remaining two open in the air. His hypothesis came true as it was observed that there were no maggots in the covered (with gauze and cork) containers but maggots were observed in the open container. He came to the conclusion that flies were able to lay their eggs on the open piece of meat and that the maggots were their offspring who grew on flesh.

Pier Antonio Micheli, an Italian botanist, performed another experiment in 1729 where he placed fungal spores on a slice of melon and observed that the same was produced on the melon slice. He concluded that the new spores definitely did not arise from spontaneous generation.

John Needham, an English biologist, did yet another experiment in 1745 with boiled broths. He infused a broth by mixing plant and animal matter and boiled it in the belief that it would kill all the microorganisms . He sealed the broth and left it for a few days. He observed that the broth had become cloudy and that it has microscopic organisms in it. He reiterated the spontaneous generation theory and many of his peers believed him. However, in reality, the broth was not boiled vigorously so as to kill all the microorganisms.

Lazzaro Spallanzani, an Italian biologist, reattempted Needham’s experiment in 1768. He took animal and plant matter-infused broths and boiled them vigorously. He kept one of the jars sealed and left the other one open to the air. According to his observations, the sealed jar was clear and did not have any growth. He then concluded that air was the force that was introducing microbes into the flask.

By this time, there was increased skepticism among scientists about the spontaneous generation theory.

In 1859, Louis Pasteur, a French microbiologist conducted another broth experiment that settled the question of spontaneous generation once and for all. He took swan flasks that had twisted necks for the experiment and boiled meat broth in it. The design of the flask was such that it allowed exchange or air from outside to inside but prevented the entry of microorganisms. If any microbes were to enter the flask they would get caught in the twisted neck of the flask. The broth remained clear for a long amount of time as long as the flask was kept intact. Once the flask was turned, which led to entry of microbes into the broth, it became cloudy.

John Tyndall, an Irish physicist, advanced the work of Louis Pasteur and finally the theory of spontaneous generation was disproved. Not much is known about Tyndall’s experiment on spontaneous generation.

In 1862, the French Academy of Sciences, announced a prize for the scientists who shed new light on the spontaneous generation controversy and appointed a jury to decide the winner. Louis pasteur was awarded the Alhumbert Prize from the Paris Academy of Sciences for his work that totally threw away the concept of spontaneous generation. 1n 1864, Pasteur was quoted saying in a lecture: “Omne vivum ex vivo” (“Life only comes from life”). Pasteur and other scientists started to use the word biogenesis for the origin of life which again meant that life comes only from another life.

This sums up the theory of spontaneous generation. Keep visiting BYJU’S Biology for more interesting topics.

Conservation of Forest and Wildlife Overview
Feedback Mechanism of Hormones
Mendel Laws of Inheritance

Who proposed the spontaneous generation theory?

What is spontaneous generation and who disproved the theory, what is the difference between cell theory and spontaneous generation, what is another name for spontaneous generation.

Register with BYJU'S & Download Free PDFs

Origins of Life I: Early ideas and experiments

by David Warmflash, MD, Nathan H Lents, Ph.D.

Listen to this reading

Did you know that it is much easier to determine when life appeared on Earth than how life came to exist? Evidence points to life on Earth as early as 3.8 billion years ago, but the question of how life came to be has puzzled scientists and philosophers since prehistoric times. In the 1950s, scientists successfully created biological molecules by recreating the atmosphere of primordial Earth in a bottle and shocking it with lightning. This and other experiments give clues to the origins of life.

Theories about the origins of life are as ancient as human culture. Greek thinkers like Anaximander thought life originated with spontaneous generation, the idea that small organisms are spontaneously generated from nonliving matter.

The theory of spontaneous generation was challenged in the 18th and 19th centuries by scientists conducting experiments on the growth of microorganisms. Louis Pasteur, by conducting experiments that showed exposure to fresh air was the cause of microorganism growth, effectively disproved the spontaneous generation theory.

Abiogenesis, the theory that life evolved from nonliving chemical systems, replaced spontaneous generation as the leading theory for the origin of life.

Haldane and Oparin theorized that a "soup" of organic molecules on ancient Earth was the source of life's building blocks. Experiments by Miller and Urey showed that likely conditions on early Earth could create the needed organic molecules for life to appear.

RNA, and through evolutionary processes, DNA and the diversity of life as we know it, likely formed due to chemical reactions among the organic compounds in the "soup" of early Earth.

The work of Darwin and Wallace went a long way in answering the question of how species evolved over time. The theory of natural selection provided a mechanism by which complex life forms, including humans, could arise from simpler organisms . But that still left open a more difficult question, namely, what is the origin of life itself? It’s one of the most challenging questions in science, even today when we can say confidently when life appeared on Earth.

Microscopic fossils called stromatolites and remains of communities of microorganisms called microbial mats suggest that Earth harbored microorganisms 3.5 billion years ago (Figure 1). Also, the presence of particular carbon isotopes in certain metamorphic rocks in Greenland tell scientists that some kind of life may have been present as much as 3.8 billion years ago. This means that 700 million to one billion years after Earth had formed, life was here. It makes sense, because it corresponds to the time when the planet had reached a cool enough temperature for any life to survive. But honing in on the time when life appeared on this planet still does not tell us how life came to exist.

Stromatolites in the Soeginina Beds of Estonia

Since prehistoric times, people sought mostly spiritual answers to this question. Around campfires during the Stone Age, each budding culture told and retold tales of how the gods created life from some kind of nonliving material, be it mud, clay, rock, or straw. The details of the ancient creation stories changed noticeably over time, but religion was still the mode of thinking by Darwin’s era when it came to the initiation of life itself. Darwin did consider the origin of life and speculated that it had occurred in a warm pond. He suggested that phosphoric salts and ammonia in the pre-biotic pond somehow had been changed chemically by heat , light , and electricity, leading to the synthesis of the organic compounds needed to produce the first living cells . Darwin was not a chemist and this was a very cursory speculation about Earth’s pre-biotic chemistry. It contrasted sharply with the detail and systematic approach of Darwin’s own theory of natural selection .

Even so, the pond idea was a start. Despite living in a society that almost universally assumed Earth had an intelligent creator, scientists in Darwin’s time were already comfortable with and accustomed to considering the possibility of life getting started without intervention from the gods. The idea was called spontaneous generation and, while it was already very well established by Darwin’s time, it dates all the way back to the time of the ancient Greeks.

Early thinkers

About 2,600 years ago, in the Ionian city of Miletus (Figure 2), the natural philosopher Anaximander (c. 610–546 BCE) pondered how human babies were born utterly helpless. Without their parents , young humans had no chance to survive and the state of helplessness continued for years. That reality made for a dilemma when considering the first generation of humans, which, Anaximander assumed, must have begun as infants. To grow up and have their own babies, human ancestors in the very distant past must have been more independent as newborns, Anaximander reasoned. They must have been more like certain other animals whose young are born ready to survive on their own.

Location of Miletus on the western coast of Anatolia

Considering the various animals, Anaximander decided the ancestors of humans had to be fish. Unlike mammals, which needed their mothers to get started in life, fish simply emerge from their eggs and either die or survive. This means that distant human ancestors could survive as infants if they were more like fish than like humans.

Even in Anaximander’s time, people saw skeletons from long-dead creatures. Fossils of extinct life were found long before paleontologists went looking for them. Ancient Greeks lived by the sea, and often the sea washed up skeletons or eroded the ground to expose buried bones. Living in this environment , Anaximander had a general idea of skeletal anatomy and how it was similar and different between humans and other animals. Because of this, he decided that the transition from fish to humans must have been gradual. In other words, humans descended from fish through an evolutionary process .

Since Anaximander proposed no idea of how the apparent evolution from fish to human had taken place, it was not an early form of Darwin’s theory of natural selection . But it was the beginning of thinking that life on Earth began with small organisms . Anaximander’s idea quickly led to the idea that small organisms were generated through a natural process from nonliving matter , such as the mud at the bottom of the sea.

Over the next centuries, Greek thinkers such as Anaximenes (588–524 BCE), Xenophanes (576–480), Empedocles (495–435), Democritus (460–370), and finally Aristotle (384–322) developed and modified the spontaneous generation idea so that it corresponded to what people often observed on land. Farmers leaving grain in an open container noticed that pretty soon mice appeared, as if the grain generated the mice. People leaving meat untended returned to find maggots infesting the meat, as if the meat generated the maggots.

Comprehension Checkpoint

Testing spontaneous generation

By the 18 th and 19 th century, the older Greek idea of spontaneous generation was well ingrained in the minds of everyone who ventured to think that the origin of life might not have required the gods. And living at a time when science was coming to age, some early modern thinkers started treating spontaneous generation less like a philosophy and more like a scientific hypothesis . Gradually, they began subjecting the idea to scientific experimentation.

An early attempt at testing spontaneous generation occurred in the 17 th century, when the Italian scientist Francesco Redi (c. 1626–1697) looked carefully at the meat-maggot phenomenon. After leaving meat in an open jar, he observed that maggots did indeed appear, and that the maggots then developed into flies, which then flew away. However, when he left meat in a sealed jar, the maggots did not appear. Nor did maggots appear when he left the meat in a jar covered with a mesh screen, a precaution he took just in case spontaneous generation required fresh air for some reason. In the terminology of today’s science, we say that the mesh-covered jar “controlled for” the possibility that spontaneous generation required fresh air (Figure 3).

Francesco Redi's spontaneous generation experiment

Since the mesh cover prevented the appearance of maggots, it meant that the maggots were not coming from spontaneous generation , but simply from eggs of adult flies. By the standards of experimental methods in contemporary science, it was a rudimentary experiment , but it was as good as it could be given the equipment available in Redi’s time.

Despite the result of his maggot experiment , Redi still believed that smaller creatures, called “gall insects” came from spontaneous generation . At the same time, a developing invention, the microscope, allowed scientists to focus on creatures even smaller: microorganisms. Using his microscope, an English experimenter, John Needham, noticed that broths made from meat were teeming with microorganisms, so he put spontaneous generation to his own test (see our module Experimentation in Scientific Research ). Needham heated a bottle of broth to kill any microorganisms, and left the bottle for a few days. Then, he looked at the broth under the microscope and found that, despite the earlier heating, the broth contained microorganisms again (Figure 4a).

Needham's spontaneous generation experiment

In Needham’s mind, this finding suggested that the lifeless broth had given rise to life. But another scientist, an Italian named Lazzaro Spallanzani , thought that Needham must have done something wrong. Perhaps, he hadn’t heated the broth to a high enough temperature or for a long enough time. To find out, Spallanzani performed his own experiment . He boiled broth in two bottles, left one bottle open and one closed, and found that new microorganisms appeared only in the open bottle. His conclusion: the microorganisms entered the bottle through the air; they were not generated spontaneously in the broth (Figure 4b).

Experiments seeming to prove or disprove spontaneous generation of life went on for another century. Because of the difference between closed and open vessels, arguments focused on the possibility that spontaneous generation of life might require fresh air. Thus, lack of air in Spallanzani’s closed bottle could have been a factor confusing the results. This possibility attracted the attention of the 19 th century’s most famous microbiologist: Darwin’s contemporary, Louis Pasteur .

Pasteur was drawn to the issue, but once involved he knew he that needed to control for the possibility that air was needed to generate life from nonliving matter . To do this, he designed flasks with long, specially curved, swanlike necks. This allowed sterilized broth to be exposed to fresh air from the outside, but any microorganisms from the air would be trapped in a pool of water in the neck. (See our module Experimentation in Scientific Research for more information on designing experiments .)

The sterilized broths in Pasteur’s special flasks did not become infested with microorganisms despite being exposed to fresh air (Figure 5). And so, after a run of more than 24 centuries, the hypothesis of spontaneous generation was finally laid to rest.

Pasteur's flask with long, swan-like necks

This meant that scientists no longer thought that microorganisms, or small animals, could suddenly emerge with no parents , but it didn’t stop people from thinking about life coming from nonliving matter . Pasteur’s publication of his experimental results disproving spontaneous generation of microorganisms came in the very same year as Darwin’s Origin of Species . This made for paradox. Around the world, scientists were fairly certain that evolution really happened, that all modern species came ultimately from pre-existing, living forms. However, as for the question of how life started in the first place, scientists had just disproved the only explanation they had.

Darwin’s pond idea was completely speculative. There was no way to test it the way he tested natural selection through years of observation of numerous species . And so, when it came to the initiation of life itself, scientists of Darwin’s era were stumped. All they could do was to throw up their hands, or chalk it up to the creation stories of their religions.

Old and new ideas

In addition to spontaneous generation , the ancient Greeks produced another idea for the origin of life on Earth: panspermia . An Ionian Greek named Anaxagoras (510–428 BCE) thought that life arrived on Earth as seedlings that came through space from other worlds. Often people think of panspermia as an alternative to the idea of life emerging from nonliving matter , but it’s actually not. Instead, panspermia only moves the origin of life off the Earth to another planet or moon, and further back in time. Thus, after Pasteur’s disproval of spontaneous generation , the motivation was stronger than ever to determine how life got started.

By the late 19th century, English biologist Thomas Henry Huxley (1825–1895) coined the term abiogenesis to describe life forms emerging from non-living chemical systems . On first hearing the term, it may sound as if abiogenesis is merely a more modern take on spontaneous generation , but there is a major difference. With spontaneous generation , the idea was that certain materials, be it meat, grain, or mud, were capable of constantly producing some kind of creature. What Huxley had in mind was the chemical reactions of life slowly emerging on the early Earth over a long period of time. Huxley knew that the mixture would have to be more complex than Darwin’s ammonia and phosphoric salts , but he did not attempt to work out the details. Somehow, though, he thought an optimal mixture of simple chemicals generated the complex chemicals needed for life, such as enzymes , and the earliest living cells .

Abiogenesis

As for how abiogenesis could occur on the primordial Earth, serious thinking about this began in the 1920s with two scientists working entirely independently of one another.

In 1922, Aleksandr Oparin, a Russian biochemist, gave a lecture on the origins of life, which was published as a booklet in 1924. For several years, the booklet was not translated from Oparin’s native Russian, so his ideas were unknown outside of the USSR. Meanwhile, British biochemist John Burdon Sanderson Haldane (usually known by his initials JBS Haldane) was working on similar ideas. Unlike his Russian counterpart, Haldane and his work were extremely visible. He was a great popularizer of science, doing for the early 20th century what astronomer Carl Sagan did later, making science understandable and fascinating for the masses. Haldane’s hands were in numerous areas of life science. He was the author of dozens of scientific papers and spent a great deal of time explaining his work and its importance to people outside the scientific world.

In connection with other questions of biology, Haldane was working with enzymes , which he thought were on the border between living and nonliving chemistry. Consequently, he hypothesized that abiogenesis took place through a complex mechanism involving enzymes and viruses. By Haldane’s time, scientists figured out that the atmosphere of the primordial Earth had been a reduced atmosphere. This means that it contained reduced carbon chemical compounds , such as methane, in contrast to oxidized chemical compounds, such as carbon dioxide (which could be present, but in much lower quantities compared with methane). It also contained hydrogen, ammonia, some water vapor, and, importantly, no oxygen.

Oxygen can come only from organisms that carry out photosynthesis to make their own food. Such organisms are called autotrophs. Haldane reasoned that the first cells must have been heterotrophs, organisms that take their food from the surrounding environment . Methane is a gas , but other simple, organic compounds made from it are liquid and would have rained down on the early Earth. They accumulated as pools of liquid on the surface , forming a kind of organic broth that became known as “Haldane’s soup” (Figure 6).

Grand Prismatic Spring in Yellowstone National Park

Because there was no oxygen in the atmosphere , the early Earth lacked a layer of ozone to block out powerful ultraviolet radiation from space. Haldane hypothesized that the ultraviolet radiation from space, along with lightning constantly hitting the primordial organic soup, delivered energy to the various simple organic compounds . This caused chemical bonds between the atoms of the molecules to break and reform, creating new and different molecules, leading to extremely large, complex organic molecules . Haldane speculated that this happened over millions of years, until finally a molecule arose that could copy itself crudely using other molecules in the “soup” as building blocks.

Molecules that could copy better than their neighbors multiplied and gradually dominated the soup. Some of these self-copying molecules became surrounded by a kind of barrier, the precursor to what we call a membrane . This happened by accident, so it was very rare, but when it did happen, Haldane explained, the enclosed, self-copying molecules had an enormous survival advantage. So they came to dominate, ate up the soup, and life had begun.

Haldane’s idea was purely hypothetical. No one tested it yet, but it was far more elaborate than Darwin’s phosphoric salt idea. Moreover, it was perfectly consistent with the state of science in the 1920s and 30s regarding the chemistry of the early Earth. Then, in 1936, Oparin’s work was finally translated from Russian. It turned out that he was proposing almost the same thing as Haldane, so the idea became known as the Oparin-Haldane hypothesis .

Putting ancient Earth into the lab

As for testing the Oparin-Haldane hypothesis , that role fell into the hands of a graduate student, Stanley Miller. In the early 1950s, Miller was looking for a thesis project in the Department of Chemistry at the University of Chicago. In 1952, his academic mentor, Professor and Nobel laureate Harold Urey, suggested that he try putting the origins of living molecules to a test. That meant recreating the kind of atmosphere that scientists thought had existed on primordial Earth: hydrogen, methane, ammonia, and water. It also meant providing what Haldane thought set the stage for creating more complicated molecules needed for life: lightning and ultraviolet light .

Once the ancient atmosphere was created and contained in a flask, Miller and Urey exposed the mixture to powerful ultraviolet light . They also put electrodes inside the flask and sent an electric current through the apparatus, creating sparks to simulate lightning, which interacted with the gases in the flask. After several days, they checked the contents of the liquid that accumulated at the bottom of the apparatus (Figure 7). They found that different molecules had been created, including various important biological molecules, such as the amino acids glycine, alanine, and valine. They ran the experiment over and over and, depending on how they changed around the gas mixture, different varieties of amino acids and other biological molecules were created. This showed that it was possible for biologically important molecules to form on a planet under abiotic conditions.

Over the years, as Miller progressed through his career, scientists studying planetary atmospheres and the ancient Earth had second thoughts about Earth’s primordial atmosphere. Perhaps it had not been dominated by methane, hydrogen, and ammonia, and possibly it could have been more oxidized as opposed to reduced. But as theories about the ancient atmosphere were refined, Miller tried variations of his original experiment with the adjusted gas mixtures . Although chemical products changed with each new mixture, in each case they included compounds that were vital to life, such as amino acids , or nitrogenous bases , the building blocks needed to make DNA and RNA . The emerging answer seemed to be that, almost regardless what the precise mixture and conditions were, complex organic molecules would result.

After the Miller-Urey experiment: Exploring proteins and membranes

While ideas about Earth’s primordial atmosphere were in flux from the 1970s onward, NASA’s exploration of the outer Solar System revealed some amazing things about the moons orbiting Jupiter and Saturn. In particular, the space probes Voyager 1 , Voyager 2 , and Cassini and an atmospheric entry probe to Saturn’s moon Titan called the Huygens probe revealed the exact makeup of Titan’s atmosphere. This inspired other scientists, such as Carl Sagan , to redo Miller’s 1952 experiment with a Titan atmospheric mixture. This too produced important biological compounds . Thus, today, the moon Titan is a prime focus for astrobiology studies in the Solar System. It may have exotic life forms, or it may be a model of how Earth was prior to life.

Several years after the original Miller-Urey experiment , another investigator, Sidney Fox, ran experiments showing that some of the Miller-Urey compounds – the amino acids – could join together to form polymers , bigger molecules known as peptides , or small proteins . This happened when amino acids made through a Miller-Urey mechanism were splashed onto surfaces of clays and other materials, under hot, dry conditions. On the ancient Earth, such conditions would have occurred at the boundary between ancient ponds or seas and ancient land. Given enough time, complex proteins could arise.

Other researchers later found that spheres of lipids (the class of organic molecules that includes fats) also could form under conditions thought to exist on the ancient Earth. This would create a water environment inside the sphere that was separated from the outside. In other words, crude membranes can form spontaneously under the same conditions in which biological compounds like amino acids and small proteins can form. The fact that membranes can form spontaneously is key to origins of life research . This is because to move from non-living chemistry to biology, very complex networks of chemical reactions need to emerge. Like a car being made on an assembly line, biological molecules are put together section by section. They also are converted into different molecules section by section, so there is a series of intermediate chemicals in addition to a starting molecule (called a substrate) and final product of each reaction .

In an open environment like Haldane’s primordial soup, or in an ocean, the various intermediates would simply diffuse away before the chemical pathway had a chance to evolve. But a membrane would enclose all of the chemicals within a compartment. That compartment would then act as a chemical laboratory, holding inside any reactions that happened to emerge. Since we know that membrane spheres can spontaneously form, the primordial soup of early Earth must have had billions of these little chemical laboratories in which the chemistry of life was sputtering along.

Moving to a DNA world

Demonstration that biological molecules and membranes can arise in an abiotic environment is not a demonstration of the emergence of life. It shows only what might have happened in the transition from non-living chemistry to the eventual formation of life. It does, however, show that a necessary step in abiogenesis – the spontaneous emergence of complex organic molecules – is not only possible, but likely under the right conditions.

Theoretically, continuous rearrangement and construction of larger and larger organic molecules from chemical building blocks that would form on the early Earth should eventually lead to molecules that can copy themselves. That’s because the bigger an organic molecule gets, the more functional chemical groups it has. Functional groups are sections of molecules with atoms other than carbon, such as oxygen, nitrogen, and phosphorus, which like to hold onto electrons . This allows for electrons to be moved around between parts of the molecule and between the molecule and other molecules. Also, the bigger a molecule gets, the more it’s able to bend and twist around. This capability, together with the capability to move around a lot of electrons, &^means it’s possible, simply by luck, for any random, very large organic molecule with a lot of nitrogen, oxygen, and phosphorus atoms to have some enzymatic capability –that is, to be able to catalyze chemical reactions .

Certain sets of reactions catalyzed by a molecule can result in the molecule making a copy of itself. Thus, with plenty of building materials in a Haldane soup, as time goes on, it is likely that self-replicating molecules would emerge. The first self-replicating molecule would have only crude copying ability. But, since it would not copy itself exactly, each new “copy” would be a little different than the “parent” molecule. Randomly, a newly copied molecule might have the ability to copy slightly better than the molecule that made it. Natural selection would then work for non-living chemical molecules similar to how Darwin described it working for living organisms . Those molecules copying better would make more copies using building blocks taken from the breakdown of other molecules that could not copy themselves so well.

Self-copying molecules enclosed in membranes would fare even better because they would be held close together with other chemicals. But for life to really begin, there has to have been a molecule whose copying ability was extremely good. Today, there is such a molecule: DNA . However, DNA is incredibly complex and this makes for a chicken and egg kind of dilemma.

In the 1980s, scientists began to realize that not all enzymes are proteins . Scientists dissected some cell components called ribosomes and found that they are made of protein and RNA . What was strange was that some of the RNA molecules actually work as enzymes. They can catalyze chemical changes in themselves and in other RNA molecules.

Like DNA , RNA can hold genetic information, but RNA is less complex than DNA (Figure 8). Consequently, a hypothesis called the “RNA world” was proposed independently by three different researchers: Leslie Orgel, Francis Crick , and Carl Woese. It’s a keystone in origins of life research today. The idea is that RNA emerged on Earth prior to DNA and was the genetic material in the first cells (or in the first cells on a different world, if life began somewhere else).

Today, no known bacterial cell or other fully-fledged life form uses RNA the way that we use DNA , as the storage molecule for genetic information. But there are RNA viruses. Not all viruses are RNA viruses; some use DNA to hold genetic instructions, just as our cells do. But if RNA is adequate as the only genetic material in some viruses, it’s easy to imagine RNA also being the only genetic material in an early bacterium, or other singled-celled creature that could have existed on the early Earth.

It’s not hard to image how the transition from RNA to DNA might have occurred. As with the evolution of everything else, there would have been mistakes. In living organisms today, DNA stores genetic information over the long term and DNA sequences are transcribed into RNA sequences, which then are used to put together sequences of amino acids into proteins (see our Gene Expression: An overview module). Essentially, DNA is an additional layer beyond RNA and the proteins that RNA makes. RNA sequences could have been the genes before a mistake created DNA. Being more stable chemically than RNA, DNA took over the job of storing genetic information. This gave RNA a chance to get better at translating genetic information into proteins.

That would have been an enormous step in life’s evolution . It also would mean that life was not here all at once. Rather, abiogenesis occurred in increments or steps during prebiotic, chemical evolution. Thus, entities must have existed along a spectrum from nonliving to living, just as viruses today have characteristics of both living and nonliving entities. We don’t know the precise abiogenesis pathway, but scientists have worked out each of the major steps necessary to go from nonliving chemistry to self-sustaining cells . Importantly, scientists also have conducted laboratory experiments demonstrating that each step is possible. Unlike the days of Anaximander , Darwin, or even Haldane, there are no big holes or theoretical barriers to abiogenesis. Scientists have a good idea of how it probably happened. Still, in terms of the details within each major step, that is where science is now focused on getting some answers.

Table of Contents

Activate glossary term highlighting to easily identify key terms within the module. Once highlighted, you can click on these terms to view their definitions.

Activate NGSS annotations to easily identify NGSS standards within the module. Once highlighted, you can click on them to view these standards.

Advertise with Us
Privacy Policy

Pasteur Brewing Louis Pasteur – Science, Health, and Brewing

Louis pasteur, francesco redi, and spontaneous generation for kids.

Where do cells come from? If a cut of meat is let out, over time it will putrefy and begin to teem with microorganisms and possibly with larger organisms like maggots. Prior to the mid-to-late 19th century, the origin of microorganisms in decaying matter was in question. Some maintained that microbes arose from other microbes that landed on the food from the air. Other supported the hypothesis of spontaneous generation, which states that living organisms can arise spontaneously from nonliving matter.

Redi’s Experiment

In the 1600’s, Francesco Redi sought to test the hypothesis of spontaneous generation by applying what came to be known as the scientific method–a process of making observations, asking questions, formulating a hypothesis and designing experiments to test the hypotheses.

Redi and others observed that flies and then maggots could be seen around pieces of meat that were left out in the open. He therefore asked the following questions: Where do flies come from? Is the rotting meat transformed into the flies? From these questions, Redi formulated the hypothesis that only flies can make flies, and that rotting meat cannot be transformed into flies.

Redi sought to test his hypothesis by performing the following experiment. He placed pieces of meat into three glass jars. The first jar was left open, the second was covered with a loos netting, and the third was completely sealed. All jars were exposed to flies in the surrounding room. Redi predicted that if meat could not be transformed into flies, then the sealed containers should not produce either maggots or flies. Whereas if the meat can be so transformed, then the sealed jar should also develop maggots and flies.

Redi recorded the presence or absence of flies and maggots in each of the three types of jars. As he predicted, neither flies nor maggots were found in the sealed jars, whereas in the open jars, maggots and flies were abundant. In the jars covered with netting, maggots were found within the netting itself, but not on the meat inside the jar. Redi concluded that meat could not transform into flies, only flies could produce flies. The theory of spontaneous generation could not be supported and was therefore incorrect.

Pasteur’s Experiment

Unfortunately, Redi’s experiment did not convince everyone. Some argued that while spontaneous generation might not apply to larger organisms like maggots and flies, it might still be applicable to smaller microbes. The question was finally answered definitively in the late 1800s by Louis Pasteur, in his now classic experiment.

Pasteur’s hypothesis was that if cells could arise from nonliving substances, then they should appear spontaneously in sterile broth.

To test his hypothesis, he created two treatment groups: a broth that was exposed to a source of microbial cells, and a broth that was not. For his control treatment, Pasteur used a straight-necked flask that allowed particles in the air to fall into the broth stored in the flask. For his experimental treatment, Pasteur used a swan-necked flask. The neck shaped and length assured that no cells could enter the broth from the air.

Swan Necked Flasks from Pasteur's Laboratory

By changing a single variable–the shape of the flask neck–Pasteur was able to conclude that cells were not generated spontaneously but were actually entering the broth from the surrounding air. Microorganisms, carried by dust particles, fell into the straight-necked flask. However, the swan neck trapped the particles, preventing cells from entering the broth.

Louis Pasteur Videos - Animated Hero Classics

Louis Pasteur Activity Book and Video for Kids

Pasteur Swan Neck Flask Experiment

Louis Pasteur Experiment: Grow Your Own Bacteria

Louis Pasteur Word Search

This word search is great for kids to learn some of the key terms used …

You must be logged in to post a comment.

The Food Untold

Discovering the Wonders of Science in Food

How Louis Pasteur Debunked the Spontaneous Generation Theory

Philosopher Aristotle coined the idea of the spontaneous generation theory in 4th century BCE, 22 centuries before time of Louis Pasteur. This theory stated that living matter could arise from non-living matter spontaneously. One of the most famous examples of this theory is that maggots could appear on decaying piece of meat.

This idea went on to persist for a very long time. This is due largely to the fact that it easily explained how mold grow on bread or that flies appear on spoiled food.

But this idea did not align to many scientists, many of them tried to disprove this idea, including Louis Pasteur.

Table of Contents

Early challenges to spontaneous generation

For a millennium, Aristotle’s theory of spontaneous generation was widely believed around the world. Was this because of the lack of technology that science enjoys today? For example, microscopes were far from being invented to allow researchers to observe and study microorganisms. Hence, experiments to test theories were not really much of a thing back then.

By the 1600, scientists and scholars have started questioning the factualness of the theory. One of these individuals who challenged the theory was Italian physician Francesco Redi. He showed that maggots do not spontaneously arise from decaying meat by doing the so-called “Redi experiment” in 1668.

Redi experiment was not sound enough to disprove the spontaneous generation theory.

In this experiment, Redi set up 3 jars of various conditions. The first jar was open and let flies to enter the jar. The second jar was tightly to prevent flies from entering. And the last jar was covered with a mesh. After letting the jars sit for a short period, maggots appeared in the open jar and mesh-covered jar, but not the tightly sealed one.

Redi concluded that flies laid eggs that would hatch into maggots. This result suggested that living matters like maggots come from other living matters, and do not arise spontaneously. Although the Redi experiment demonstrated that living matters could only arise from pre-existing living matters, this was not sound enough to disprove the spontaneous generation theory.

Hence, the debate continued.

Antonie Van Leeuwenhoek contribution

Antonie Van Leeuwenhoek was a Dutch scientist known as the Father of Microbiology. He developed microscopes during the 17th century that were considered advance during that time. Leeuwenhoek made about 500 microscopes in this career. One of these could magnify objects up to 300 times. This capability was unrivaled back then. In comparison, the microscope English physicist Robert Hooke developed could only magnify up to 50 times. This magnification could only reveal basic details on minute organisms.

Leeuwenhoek’s, on the other hand had greater magnification. This allowed him to study various microorganisms in greater detail. Leeuwenhoek described bacteria, yeasts, and other microorganisms. Their shapes, movement, and behavior were documented for the first time. But his discovery of the existence of microorganisms was not solid evidence to dispel the spontaneous generation theory.

You might also like: The Bacteria That Make Limburger Cheese Smell

When his work was made public, scientist still wondered the same question. Do microorganisms come from pre-existing living things? Or they just generate spontaneously from non-living things? Yes, the scope of microbiology back then was very limited. However, Leeuwenhoek’s contribution to understanding microorganisms paved the way for another scientist to disprove the theory of spontaneous generation at once, Louis Pasteur.

Louis Pasteur’s works prior to debunking the spontaneous generation theory

Louis Pasteur was a French chemist and microbiologist. He lived during the 19th century. At this point, the debate on the spontaneous generation theory was at its peak. Prior to disproving the theory, he already worked on fermentation, and pasteurization.

In 1850s, Pasteur studied extensively the process of fermentation. Fermentation is a preservation method wherein sugar in food is converted into alcohol or acid. Prior to Pasteur’s research on the process, it was widely accepted that fermentation was solely a chemical process. The belief was that fermentation would occur because components in food decompose in the absence of air. Hence, microorganisms were not believed to be responsible in fermentation.

But Pasteur’s work changed this when he studied spoilage in wine and beer. In the mid-19th century, the brewing industry in France was suffering from economic losses due to spoilage of wine. The losses were massive that it hit wine exports badly. To resolve the problem, Napoleon III and the French government asked for help from Pasteur. He then presented clear evidence that undesirable or spoilage microorganisms were responsible for the off-flavor and souring in wine.

What Pasteur did was preheat the wine at between 122°F (50°C) and 140°F (140). This prevented souring and extended the shelf life of wine.

Based on his research on microorganisms, spoilage microorganisms found in wine are heat sensitive. Hence, he hypothesized that treating the wine with elevated heat high enough to destroy these microbes would effectively extend the shelf life of wine. The temperature range he used was well thought of because not only it killed unwanted microbes, but it was also not high enough to preserve the flavor of the wine. This heat treatment is now called pasteurization.

Pasteur’s Swan-Neck Flask experiment debunked the spontaneous generation

Louis Pasteur became aware of the spontaneous generation when he came to know fellow Frenchmen Felix Archimède Pouchet, a strong follower of the spontaneous generation theory. Pasteur had been very skeptical about the theory, and the French Academy of Sciences opened a competition called Alhumbert Prize to ultimately put an end to this debate. Pasteur took up the challenge and performed an experiment that would ultimately debunk the theory— the Swan-Neck flask experiment.

In this experiment, Pasteur gathered a number of long, curved S-shaped flasks that looked like swan’s neck, hence the name of the experiment. He filled each flask with an infusion or nutrient rich broth. After that, he pasteurized the flasks to destroy the harmful microorganisms that were present in the broth.

After letting the pasteurized broth in the flask to sit for some time he observed what happened. And just as he predicted, the broth did not change in appearance or appear to have been contaminated. The unique S-shape of the flask prevented contaminated to happen here. The curve neck allowed air to flow through, but not dust and any other elements that may contaminate the broth.

But if the curved long neck of the flasks were removed, or the flask were tilted that the broth got into contact with the curve neck, airborne microorganisms would have been introduced to the broth and contaminate it.

The Swan-Neck flask experiment by Pasteur ultimately debunked the spontaneous generation theory. Because of this, he was awarded the Alhumbert prize, which also carried a value of 2,500 francs. This was considered a huge sum already in 1862.

← What Is Vacuum Packaging In Food Preservation?

Water Activity (aw) And Food Safety

Factors That Affect Growth of Harmful Microorganisms

Can You Really Reheat Leftover Rice?

IMAGES

Pasteurization Louis Pasteur Invented
Pasteur's Experiment
Louis Pasteur and his contributions
Louis Pasteur Invented Pasteurisation
Louis Pasteur Experiment
Spontaneous Generation: A Brief History Of Disproving It.

VIDEO

Unveiling Louis Pasteur: A Short Biography 🌟 #shorts #history #facts #youtubeshorts #trending #story
Louis Pasteur experiment #neet2024 #biology #neet #shortsvideo #shorts #rapidrevision #viralvideo
Louis Pasteur Experiment #evolution # Origin Of Life#(12 class)
Pasteur's experiment
Day 4: Raw Chicken Experiment
Lab Meat: Experiment on Your Plate

COMMENTS

Pasteur's Experiment
Pasteur's experiment helped solidify the steps of the scientific method. Learn about the steps of Pasteur's experiment and what Pasteur's experiment proved.
Spontaneous generation
Louis Pasteur 's 1859 experiment is widely seen as having settled the question of spontaneous generation. [47] He boiled a meat broth in a swan neck flask; the bend in the neck of the flask prevented falling particles from reaching the broth, while still allowing the free flow of air. The flask remained free of growth for an extended period.
Louis Pasteur
Pasteur suspected that the agent that caused rabies was a microbe (the agent was later discovered to be a virus, a nonliving entity). It was too small to be seen under Pasteur's microscope, and so experimentation with the disease demanded the development of entirely new methodologies. Pasteur chose to conduct his experiments using rabbits and transmitted the infectious agent from animal to ...
3.1 Spontaneous Generation
The Greek philosopher Aristotle (384-322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion th...
Spontaneous generation
Spontaneous generation, the hypothetical process by which living organisms develop from nonliving matter; also, the archaic theory that utilized this process to explain the origin of life. Many believed in spontaneous generation because it explained such occurrences as the appearance of maggots on decaying meat.
2.1 Spontaneous Generation
Figure 2.4 (a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur 's experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur's experiment consisted of two parts.
SPONTANEOUS GENERATION (ABIOGENESIS)
A French chemist and microbiologist, Pasteur used the swan-necked flask experiment (Figure 2) to disprove the theory of spontaneous generation. Louis Pasteur improved on the works of Needham and Spallanzani by boiling meat broth in bent-flasks which was opened to the air.
Louis Pasteur, Spontaneous Generation, and Germ Theory
What Pasteur did was put the belief of spontaneous generation to rest with a simple, yet brilliant experiment. Pasteur boiled some nutrient broth inside a flask with a long, twisted neck. The ...
Spontaneous generation was an attractive theory to many people, but was
Louis Pasteur ended the debate with his famous swan-neck flask experiment, which allowed air to contact the broth. Microbes present in the dust were not able to navigate the tortuous bends in the neck of the flask.
Spontaneous Generation
Spontaneous generation, also called abiogenesis, is the belief that some living things can arise suddenly, from inanimate matter, without the need for a living progenitor to give them life. In the fourth century B. C., the Greek philosopher and scientist Aristotle argued that abiogenesis is one of four means of reproduction, the others being ...
Is Spontaneous Generation Real?
The Pasteur experiment was the most famous experiment conducted that disproved spontaneous generation that was accepted by the majority of the scientific community. Pasteur demonstrated that bacteria appearing in broth are not the result of spontaneous generation.
Experiments in support and against Spontaneous Generation
Louis Pasteur's 1859 experiment is widely seen as having settled the question of spontaneous generation. He boiled a meat broth in a flask that had a long neck that curved downward, like that of a goose or swan. The idea was that the bend in the neck prevented falling particles from reaching the broth, while still allowing the free flow of air.
The middle years 1862-1877
Spontaneous generation - the big debateAt the time the spontaneous generation theory was widely accepted in scientific circles. Louis Pasteur decided to approach the issue via his experimental method.This required the use of swan-necked flasks. Water in the flask was brought to the boil for a few minutes until the steam escaped from the open end of the flask. It was then left to cool. While ...
3.1 Spontaneous Generation
Figure 3.4. (a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur's experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur's experiment consisted of two parts.
Spontaneous Generation Theory
By this time, there was increased skepticism among scientists about the spontaneous generation theory. In 1859, Louis Pasteur, a French microbiologist conducted another broth experiment that settled the question of spontaneous generation once and for all. He took swan flasks that had twisted necks for the experiment and boiled meat broth in it.
Spontaneous Generation
By 1860, the debate had become so heated that the Paris Academy of Sciences offered a prize for any experiments that would help resolve this conflict. The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in these microscopic organisms.
Origins of Life I: Early ideas and experiments
Since prehistoric times, people have pondered how life came to exist. This module describes investigations into the origins of life through history, including Louis Pasteur's experiments that disproved the long-held idea of spontaneous generation and and later research showing that the emergence of biological molecules from a nonliving environment - or abiogenesis - is not only possible ...
Louis Pasteur, Francesco Redi, and Spontaneous Generation for Kids
Redi's Experiment In the 1600's, Francesco Redi sought to test the hypothesis of spontaneous generation by applying what came to be known as the scientific method-a process of making observations, asking questions, formulating a hypothesis and designing experiments to test the hypotheses. Redi and others observed that flies and then maggots could be seen around pieces of meat that were ...
How Louis Pasteur Debunked the Spontaneous Generation Theory
Philosopher Aristotle coined the idea of the spontaneous generation theory in 4th century BCE, 22 centuries before time of Louis Pasteur. This theory stated that living matter could arise from non-living matter spontaneously. One of the most famous examples of this theory is that maggots could appear on decaying piece of meat.

How the Scientific Method Works

Pasteur's Experiment

3.1 Spontaneous Generation

Clinical Focus

The Theory of Spontaneous Generation

Check Your Understanding

Disproving Spontaneous Generation

spontaneous generation

2.1 Spontaneous Generation

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

Share This Book

SPONTANEOUS GENERATION (ABIOGENESIS)

Share this:

Related Posts

Introduction to (Medical) Bacteriology

Microbial Growth

Louis Pasteur, Spontaneous Generation, and Germ Theory

Life Comes From Life

Related Posts

Recent news

Possible First-Ever Sighting of a Great White Shark Birth Stuns Researchers

Scientists Revive 1,000-Year-Old Seed, Potentially Resurrecting Mysterious Biblical Tree

Meet the Sea Robin: A Fish That Walks and Tastes the Seafloor With Its Legs

Latest News

Learning Objectives

Table 1.3 Events in spontaneous generation

Key Takeaways

Is Spontaneous Generation Real?

Key Takeaways

Do Animals Spontaneously Generate?

Spontaneous Generation Debate

Redi Experiment

Needham Experiment

Spallanzani Experiment

Pasteur Experiment

Experiments in support and against Spontaneous Generation

Experiments in Support of Spontaneous Generation

John Needham

Experiments against Spontaneous Generation

Francesco Redi

Lazzaro Spallanzani

Louis Pasteur

John Tyndall

Leave a Comment Cancel reply

The middle years 1862-1877

Spontaneous generation - the big debate

So how does fermentation work ?

To the rescue of industry and agriculture

Wine diseases

Silkworm diseases

3.1 Spontaneous Generation

CLINICAL FOCUS: Part 1

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

Multiple Choice

Critical Thinking

Media Attributions

Share This Book

Spontaneous Generation Theory

Aristotle’s Work

Who proposed the spontaneous generation theory?

Register with BYJU'S & Download Free PDFs

Origins of Life I: Early ideas and experiments

Comprehension Checkpoint

Pasteur Brewing Louis Pasteur – Science, Health, and Brewing

Redi’s Experiment

Pasteur’s Experiment

Related Articles

Louis Pasteur Activity Book and Video for Kids

Pasteur Swan Neck Flask Experiment

Louis Pasteur Experiment: Grow Your Own Bacteria

Louis Pasteur Word Search

Leave a Reply

The Food Untold

How Louis Pasteur Debunked the Spontaneous Generation Theory

Early challenges to spontaneous generation

Antonie Van Leeuwenhoek contribution

Louis Pasteur’s works prior to debunking the spontaneous generation theory

Pasteur’s Swan-Neck Flask experiment debunked the spontaneous generation