103
See also: Classification of living things 82–83 ■ The microbiological
environment 84–85 ■ The ecosystem 134 –137THE VARIETY OF LIFE
As he extended germ theory to
human disease, Pasteur proposed
that germs invade the body and
cause specific disorders. Edward
Jenner, nearly 100 years before,
had shown that a disease could be
prevented with the application of
a “vaccine”—a virus similar to that
of the disease-causing microbe.
Pasteur found that an attenuated,
or weakened, form of a disease-
causing germ, produced in a
laboratory and injected into the hostanimal or human, was particularly
effective at enabling the body’s
immune system to fight off the
disease. At first, Pasteur faced
strong opposition and alarm at
the prospect, but he was able to
develop vaccines for anthrax, fowl
cholera, and rabies—the latter
involving his first test on a human.Annihilating germs
The focus later shifted to finding
germ-killing agents, or antibiotics,
such as penicillin—discovered by
Alexander Fleming. A strategy of
annihilating microbes has been
followed ever since. Yet this
“slash and burn” approach has
its drawbacks. It kills beneficial
microbes as well as harmful ones,
and also promotes resistance in
bacteria that can ultimately render
antibiotics ineffective. ■Louis Pasteur
Born in Dole, France, in 1822,
Pasteur was the son of a poor
tanner. He was an average
student, but he worked hard,
obtaining his degree in 1842
and his doctorate in science
in 1847. After teaching in
various universities, in 1867
he became Professor of
Chemistry at the Sorbonne
in Paris. His major research
interest was the fermentation
process. Pasteur discovered
that the fermentation of wine
and beer was caused by
germs—microbes. He also
discovered that microbes
could be killed by short, mild
heat treatment—a process
now named after him as
“pasteurization.” Pasteur’s
“germ theory” led to the wider
development of vaccines,
which remain a vital method
of disease control. In 1887,
he established the Pasteur
Institute, which opened in
1888 and continues to help
prevent and fight diseases.
Key works1870 Studies on Silk Worm
Disease
1878 Microbes: Their Role in
Fermentation, Putrefaction,
and the Contagion
1886 Treatment of RabiesThe bacterium Enterococcus faecalis
is a microbe found in the gut and bowel
of healthy humans. If it spreads to other
areas of the body, however, it can cause
serious infections.Where observation
is concerned,
chance favors only
the prepared mind.
Louis PasteurUS_102-103_Microbiology.indd 103 12/11/18 6:24 PM