Germs from Nowhere: Spontaneous Generation

Germs from Nowhere
Spontaneous Generation

Antonie van Leeuwenhoek

Microorgansims were first discovered about 250 years ago. Antonie van Leeuwenhoek (1632-1723), a Dutch civil servant, learned how to make excellent lenses from which he also built some of the earliest microscopes. Leeuwenhoek used his microscope to look at lots of different things, including drops of water. When he looked at water drops magnified many times, he saw bacteria swimming among the many “little animals” under his lenses. Throughout the 1700s there was much speculation about the origin of microbes that also were found in decaying (putrefying) meat and meat products such as broth, as well as in fermenting fruit juices. The question was, “Do the microbes cause decay and fermentation, or are the microbes produced by decay and fermentation?” Does life come from life or is it produced spontaneously? If life produces life, what is the source of the parent material? Biologists were faced with the old question of which came first, the chicken or the egg? Answering the question through simple observation was difficult since bacteria and other microscopic organisms were too small to see unless using a microscope. But the issue of spontaneous generation became a major controversy for scientists during the 1700s.

Van Leeuwenhoek's
microscope.

An English Catholic priest, John Tuberville Needham (1713-1781), attempted in 1748 to demonstrate that spontaneous generation really happened. Using meat broth that had been sterilized and sealed off from the air, Needham observed microorganisms growing in the culture medium. The experiment was criticized in 1767 by the Italian scientist Lazzaro Spallanzani (1729-1799). He demonstrated with experiments that Needham most likely did not completely sterilize the broth medium. Spallanzani used various sterilization times to show clearly that growth of microbes would not occur if culture medium was sterilized for at least 45 minutes in boiling water. There was still an issue concerning the sterility of the air trapped in the vessel, something that was not resolved experimentally until some years later. Needham felt that the excessive heating altered the air itself as well as destroying a “vegetative force” preventing spontaneous generation. Since Needham thought there were no microbes in the culture medium at the beginning of the experiment, he dismissed the idea that no microbes grew in a sterilized medium because heating had simply killed them all.

Lazzaro Spallanzani

Spallanzani did not resolve the question about the alteration of the air in the sealed and heated containers. Later chemists such as Gay-Lussac were able to show that oxygen was missing from the “air” remaining in the heated and sealed vessels and it was this absence of air that would prevent the appearance of “spontaneous” life. What was needed then were experiments to differentiate between the effects of anaerobic, or oxygen-free, “air” and the destruction of microbes with heat. Such was the work of Louis Pasteur as documented in his Memoirs of 1862, Chapter IV. His experimental setup can be repeated with some equipment modifications as outlined below. (Pasteur's original flasks still exist at the Pasteur Museum in Paris, complete with uncontaminated broth in those containers designed to prevent microbial growth).

Louis Pasteur

Pasteur works in Whitbread's laboratory, 1871.

For more information, at other Web sites...

Antonie van Leeuwenhoek — short biography, part of Molecular Expressions created by Michael W. Davidson and Florida State University.
Lazzaro Spallanzani — a short biography from Ole Daniel Enersen's Whonamedit.com.
Louis Pasteur — in-depth biographical site created and hosted by David V. Cohn, Ph.D., Professor of Biochemistry, University of Louisville.
Pasteur Museum — official site of the Pasteur Museum in Paris, with information on Pasteur's life and work as well as many images.

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Image Credits

Antonie van Leeuwenhoek: Courtesy National Library of Medicine.
Van Leeuwenhoek's microscope: Courtesy U.S. Armed Forces Medical Museum.
Lazzaro Spallanzani: Courtesy National Library of Medicine.
Louis Pasteur: Protrait by Fernand Desmoulin, part of the Fisher Collection, Chemical Heritage Foundation, photoghraphed by Will Brown.
Pasteur works in Whitbread's laboratory, 1871: Protrait by Fernand Desmoulin, part of the Fisher Collection, Chemical Heritage Foundation, photoghraphed by Will Brown.

Copyright ©2002 The Chemical Heritage Foundation