Louis Pasteur was born in Dole, France, the son of a tanner.
In his early work as a chemist he resolved a problem concerning the nature of tartaric acid. A solution of this compound derived from one source rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by synthesis had no such effect, even though its reactions were identical and its composition was the same.
Pasteur noticed, upon examination of the tiny crystals of tartaric acid, that the crystals came in two asymmetric forms that were mirror images of one another. Tediously sorting the crystals by hand gave two forms of tartaric acid: solutions of one form rotated polarised light clockwise; the other form rotated light anticlockwise; and an equal mix of the two had no effect on polarized light. Pasteur correctly deduced that the tartaric acid molecule was asymmetric and could exist in two different forms that resemble one another as a left- and right-hand glove resemble one another. As the first demonstration of chiral molecules, it was quite an achievement, but Pasteur then went on to his more famous work in the field of biology/medicine.
He demonstrated that fermentation and the growth of microorganisms in nutrient broths were not due to spontaneous generation. He exposed freshly boiled broths to air in vessels that contained a filter to prevent all particles from passing through to the growth medium and even in vessels with no filter at all, with air being admitted via a long tortuous tube that would not allow dust particles to pass. Nothing grew in the broths; therefore, the living organisms that grew in such broths came from outside, as spores on dust, rather than being spontaneously generated within the broth.
With this established, he invented the process of pasteurization, in which liquids such as milk were heated to kill all bacteria and molds already present within them.
His later work on diseases included work on chicken cholera. During this work, a culture of the responsible bacteria had spoiled and failed to induce the disease in some chickens he was infecting with the disease. Upon reusing these healthy chickens, Pasteur discovered that he could not infect them, even with fresh bacteria: the weakened bacteria had caused the chickens to become immune to the disease, although they had not actually caused the disease.
The notion of a weak form of a disease causing immunity to the virulent version was not new: this had been known for a long time for smallpox. Inoculation with smallpox was known to result in far less scarring and greatly reduced mortality than with the naturally acquired disease. Edward Jenner had also discovered vaccination, using cowpox to give cross-immunity to smallpox, and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference with chicken cholera was that the weakened form of the disease organism had been generated artificially, and so a naturally weak form of the disease organism did not need to be found.
This discovery revolutionised work in infectious diseases, and Pasteur gave these artificially weakened diseases the generic name of vaccines, to honour Jenner's discovery. Pasteur produced the first vaccine for rabies, which was first used on 9-year old Joseph Meister on July 6, 1885 after the boy was badly mauled by a rabid dog. This was done at some personal risk for Pasteur, since he was not a licensed doctor and could have faced prosecution for treating the boy. Fortunately, the treatment proved to be a spectacular success, with the boy avoiding the disease. So Pasteur was hailed as a hero and the legal matter was not pursued. The treatment's success laid the foundations for the manufacture of many other vaccines. The first of the Pasteur Institutes[?] was also built on the basis of this achievement.
Pasteur died in 1895 from complications caused by a series of strokes that had begun plaguing him as far back as 1868. He was buried in the Cathedral of Notre Dame, but his remains were soon placed in a crypt in the Institut Pasteur[?], Paris.
Also work on anthrax, silk worm diseases and brewing that I can't remember offhand. Perhaps someone else can fill in.
His work with silk: In 1865, Pasteur set out to help the silk industry. A disease called pebrine was killing great numbers of silkworms. He worked several years to prove that a microbe that attacks silkworm eggs causes the disease. He showed that eliminating this germ in silkworm nurseries would wipe out the disease.
If they'd had the Nobel Prize back then, there's no doubt Louis would have been a hot contender for the Chemistry, Biology and Medicine prizes. He did, however, win the Leeuwenhoek medal, microbiology's highest honor, in 1895.