Louis Pasteur Biography (1822-1895)

chemist, microbiologist

Louis Pasteur was one of the most extraordinary scientists in history, leaving a legacy of scientific contributions which include an understanding of howmicroorganisms carry on the biochemical process of fermentation, the establishment of the causal relationship between microorganisms and disease, and theconcept of destroying microorganisms to halt the transmission of communicabledisease. These achievements led him to be called the founder of microbiology.

After his early education Pasteur went to Paris, studied at the Sorbonne, then began teaching chemistry while still a student. After being appointed chemistry professor at a new university in Lille, France, Pasteur began work on yeast cells and showed how they produce alcohol and carbon dioxide from sugar during the process of fermentation. Fermentation is a form of cellular respiration carried on by yeast cells, a way of getting energy for cells when thereis no oxygen present. He found that fermentation would take place only when living yeast cells were present.

Establishing himself as a serious, hard-working chemist, Pasteur was called upon to tackle some of the problems plaguing the French beverage industry at the time. Of special concern was the spoiling of wine and beer, which caused great economic loss and tarnished France's reputation for fine vintage wines.Vintners wanted to know the cause of l'amer, a condition that was destroyingthe best burgundies. Pasteur looked at wine under the microscope and noticedthat when aged properly the liquid contained little spherical yeast cells. But when the wine turned sour, there was a proliferation of bacterial cells which were producing lactic acid. Pasteur suggested that heating the wine gentlyat about 120°F would kill the bacteria that produced lactic acid and letthe wine age properly. Pasteur's book Etudes sur le Vin, published in1866 was a testament to two of his great passions--the scientific method andhis love of wine. It caused another French Revolution--one in wine-making, as Pasteur suggested that greater cleanliness was need to eliminate bacteria and that this could be done with heat. Some wine-makers were aghast at the thought but doing so solved the industry's problem.

The idea of heating to kill microorganisms was applied to other perishable fluids like milk and the idea of pasteurization was born. Several decades laterin the United States the pasteurization of milk was championed by American bacteriologist Alice Catherine Evans who linked bacteria in milk with the disease brucellosis, a type of fever found in different variations in many countries.

In his work with yeast, Pasteur also found that air should be kept from fermenting wine, but was necessary for the production of vinegar. In the presenceof oxygen, yeasts and bacteria break down alcohol into acetic acid--vinegar.Pasteur also informed the vinegar industry that vinegar production could be increased by adding more microorganisms to the fermenting mixture. Pasteur carried on many experiments with yeast. He showed that fermentation can take place without oxygen (anaerobic conditions), but that the process still involved living things such as yeast. He did several experiments to show (as Lazzaro Spallanzani had a century earlier) that living things do not arise spontaneously but rather come from other living things. To disprove the idea ofspontaneous generation, Pasteur boiled meat extract and left it exposed to air in a flask with a long S-shaped neck. There was no decay observed because microorganisms from the air did not reach the extract. On the way to performing his experiment Pasteur had also invented what has come to be known as sterile technique, boiling or heating of instruments and food to prevent the proliferation of microorganisms.

In 1862 Pasteur was called upon to help solve a crisis in another ailing French industry. The silkworms that produced silk fabric were dying of an unknowndisease. So armed with his microscope, Pasteur went to the south of France in 1865. He found the tiny parasites that were killing the silkworms and affecting their food, mulberry leaves. His solution seemed drastic at the time. Hesuggested destroying all the unhealthy worms and starting with new cultures.The solution worked and French silk scarves were back in the marketplace.

Pasteur then turned his attention to human and animal diseases. He had believed for some time that microscopic organisms cause disease and that these tinymicroorganisms could travel from person to person spreading the disease. Other scientists had expressed this thought before, but Pasteur had more experience using the microscope and identifying different kinds of microorganisms such as bacteria and fungi.

In 1868, Pasteur suffered a stroke and much of his work thereafter was carried out by his wife Marie Laurent Pasteur. After seeing what military hospitalswere like during the Franco-Prussian War, Pasteur impressed upon physiciansthat they should boil and sterilize their instruments. This was still not common practice in the nineteenth century.

Pasteur developed techniques for culturing and examining several disease-causing bacteria. He identified Staphylococcus pyogenesbacteria in boils and Streptococcus pyogenes in puerperal fever. He also cultured the bacteria that cause cholera. Once when injecting healthy chickens with cholera bacteria, he expected the chickens to get sick. Unknown to Pasteur, the bacteria were old and no longer virulent. The chickens failed to get the disease, but instead they received immunity against cholera. Thus Pasteur discovered that weakened microbes make a good vaccine by imparting immunity without actually producing the disease.

Pasteur then began work on a vaccine for anthrax, a disease that killed manyanimals and infected people who contracted it from their sheep and thus was known as "woolsorters' disease." Anthrax causes sudden chills, high fever, pain, and can affect the brain. Pasteur experimented with weakening or attenuating the bacteria that cause anthrax, and in 1881 produced a vaccine that successfully prevented the deadly disease.

Pasteur's last great scientific achievement was developing a successful treatment for rabies, a deadly disease contracted from bites of an infected, rabiddog. Rabies, or hydrophobia, first causes terrible pain in the throat that prevents swallowing, then brings on spasms, fever, and finally death. Pasteurknew that rabies took weeks or even months to become active. He hypothesizedthat if people were given an injection after being bitten, it could prevent the disease from manifesting. After methodically producing a rabies vaccine from the spinal fluid of infected rabbits, Pasteur sought to test it. In 1885 nine-year-old Joseph Meister, who had been mauled and bitten by a rabid dog, was brought to Pasteur, and after a series of shots of the new rabies vaccine,the boy did not develop any of the deadly symptoms of rabies. Pasteur's triumphant success was a great relief to many worldwide.

To treat cases of rabies, the Pasteur Institute was established in 1888 withmonetary donations coming from all over the world. It later became one of themost prestigious biological research institutions in the world. When Pasteurdied in 1895 he was well-recognized for his outstanding achievements in science.

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