Louis Pasteur

French microbiologist 1822-1895

Louis Pasteur was a French microbiologist who made major discoveries about the biology of bacteria; invented techniques to prevent the spoilage of milk, wine, and beer by microorganisms; and pioneered the prevention of infectious disease through vaccination.

Pasteur was born in 1822 in Dole, France. He studied physical sciences at a prominent teachers’ college in Paris and, at the age of twenty-six, pre­sented his first significant research results to the Paris Academy of Sciences. Pasteur had discovered that a certain chemical could form two different crys­tals, whose shapes were mirror images of each other. Pasteur proposed, cor­rectly, that this difference reflected a molecular difference, and that the two forms of the molecule had the same relationship as the left and right hands, being similar in form but opposite in orientation of parts. Pasteur showed that many molecules display this property, and that often only one form can be used by living organisms for food. This mirror-image property (called chirality) was later shown to be possessed by virtually every molecule of bi­ological importance, including the amino acids that make up proteins.

In 1854, Pasteur was appointed dean of the Science Faculty at the Uni­versity of Lille, where he offered evening classes to local workmen and in­troduced his day students to the foreign world of the industrial factories of Lille, demonstrating to both groups the connection between scholarship and industry he believed would profit them both. Pasteur became deeply in­volved in the study of fermentation, the process by which grape juice be­comes wine, grain mash becomes beer, and milk sours. Back in Paris several years later, Pasteur showed that microorganisms (yeasts and bacteria) were responsible for the fermentation process, and that fermentation could be ac­celerated or retarded by changing the conditions of the liquid in which it occurred. He invented the process of preserving milk and other drinks by heating, which killed the microorganisms within, a process called pasteur­ization in his honor. In the following years, he discovered a bacterium threat­ening the French silk industry and devised procedures to identify and destroy infected silkworms.

Pasteur also played a critical role in a theoretical debate of the time, that of spontaneous generation. Proponents argued that the rank growth produced in standing water was due to creation of new organisms from inan­imate matter. By first boiling the water and then excluding any airborne sources of contamination, Pasteur showed the water remained clear. Thus the most likely source of growth was preexisting microorganisms, not the spontaneous generations of new ones.

At age fifty-two, Pasteur was given financial security by the French par­liament, allowing him to continue his researches without worry about in­come. At age fifty-nine, he devoted himself to vaccination, the process of disease prevention invented by Englishman Edward Jenner in 1796. Jenner had prevented smallpox infection by inoculation with cowpox, a related but less harmful organism. Not all virulent organisms have such relatives, though, and so the problem faced by Pasteur was how to weaken the infec­tious organism so it could be used as the vaccine. Pasteur discovered that storing cultures under various conditions for weeks to months accomplished this, and he used this technique to develop vaccines for anthrax in sheep and rabies in humans. He first used the rabies vaccine on July 6, 1885, to cure a young boy bitten by a rabid dog. Pasteur saved the boy’s life, and earned international fame in the process. Pasteur became the head of the Pasteur Institute in 1888, where he remained until his death in 1895.

References

Magner, L. N. History of the Life Sciences. New York: Marcel Dekker, 1994.