Louis Pasteur





Louis Pasteur (December 27, 1822 - September 28, 1895)
was a French scientist who was a pioneer in microbiology.

Louis Pasteur was born in Dole, Jura dŽpartement, France, the son of a
tanner. He was admitted in 1843 at the ƒcole Normale SupŽrieure and got a
doctoral degree in 1846.

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.

His doctoral thesis on cristallography got him a position of professor of
chemistry at the FacultŽ (College) of Strasbourg.

In 1854, he was named Dean of the new College of Science in Lille. In 1857,
he was made administrator and director of scientific studies of the ƒcole
Normale SupŽrieure.

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 physician 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.