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Early life and biography

Louis Jean Pasteur was born on December 27, 1822 in Dole in the Jura region of France and grew up in the town of Arbois. There he later had his house and laboratory, which is a Pasteur museum today. His father, Jean Pasteur, was a poorly educated tanner and a veteran of the Napoleonic wars. Louis's aptitude was recognized by his college headmaster, who recommended that the young man apply for the Ecole Normale superieure, which accepted him. After serving briefly as professor of physics at Dijon Lycée in 1848, he became professor of chemistry at Strasbourg University, where he met and courted Marie Laurent, daughter of the university's rector in 1849. They were married on May 29, 1849 and together they had five children, only two of whom survived to adulthood. Throughout his whole life, Louis Pasteur remained an ardent Catholic. A well-known quotation illustrating this is attributed to him: "The more I know, the more nearly is my faith that of the Breton peasant. Could I but know all I would have the faith of a Breton peasant's wife.

Work on chirality and the polarization of light

In Pasteur's early works as a chemist, he resolved a problem concerning the nature of tartaric acid (1849). A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by chemical synthesis had no such effect, even though its chemical reactions were identical and its elemental composition was the same.

Upon examination of the minuscule crystals of Sodium ammonium tartrate, Pasteur noticed 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 the compound: solutions of one form rotated polarized light clockwise, while the other form rotated light counterclockwise. An equal mix of the two had no polarizing effect on light. Pasteur correctly deduced the molecule in question was asymmetric and could exist in two different forms that resemble one another as would left- and right-hand gloves, and that the biological source of the compound provided purely the one type.This was the first time anyone had demonstrated chiral molecules.

Pasteur's doctoral thesis on crystallography attracted the attention of M. Puillet and he helped Pasteur garner a position of professor of chemistry at the Faculté (College) of Strasbourg.

In 1854, he was named Dean of the new Faculty of Sciences in Lille. In 1856, he was made administrator and director of scientific studies of the École Normale Supérieure.

Germ theory

Louis demonstrated that the fermentation process is caused by the growth of microorganisms, and that the growth of microorganisms in nutrient broths is not due to spontaneous generation but rather to biogenesis (Omne vivum ex ovo).

He exposed 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 spontaneously generated within the broth. This was one of the last and most important experiments disproving the theory of spontaneous generation. The experiment also supported germ theory.

While Pasteur was not the first to propose germ theory (Girolamo Fracastoro, Agostino Bassi, Friedrich Henle and others had suggested it earlier), he developed it and conducted experiments that clearly indicated its correctness and managed to convince most of Europe it was true. Today he is often regarded as the father of germ theory and bacteriology, together with Robert Koch.

Pasteur's research also showed that some microorganisms contaminated fermenting beverages. With this established, he invented a process in which liquids such as milk were heated to kill most bacteria and molds already present within them.He and Claude Bernard completed the first test on April 20, 1862. This process was soon afterwards known as pasteurisation (or "pasteurization" in America).

Beverage contamination led Pasteur to conclude that microorganisms infected animals and humans as well. He proposed preventing the entry of microorganisms into the human body, leading Joseph Lister to develop antiseptic methods in surgery.

In 1865, two parasitic diseases called Pébrine and flacherie were killing great numbers of silkworms at Alais (now Alès). Pasteur worked several years proving it was a microbe attacking silkworm eggs which caused the disease, and that eliminating this microbe within silkworm nurseries would eradicate the disease.

Pasteur also discovered anaerobiosis, whereby some microorganisms can develop and live without air or oxygen, called the Pasteur effect.