102
M
icrobes—bacteria,
molds, viruses, protozoa,
and algae—are present
in every environment, living in soil,
water, and air. Some microbes
cause disease but most are vital for
life on Earth. Among other things,
they break down organic matter so
that it can be recycled back into
the ecosystem.
Trillions of microbes also live on
and in the human body. The most
common of these microbes are
beneficial bacteria, which aid the
digestion of food, produce vitamins,
and help the immune system find
and attack more harmful microbes.Scientists did not understand
microbes until they could see them.
The first observations began in the
17th century, using the recently
invented microscope. These
studies revealed a previously
unknown world teeming with
microbiotic life. Around the same
time, the word “germ,” originally
meaning “seed,” was first used
to describe these tiny organisms.Fighting disease
Some 17th and 18th-century
scientists believed that certain
“germs” might cause diseases, but
the prevailing view was that such
maladies were the spontaneous
result of inherent weakness in an
organism. It was not until the
painstaking laboratory work of the
19th-century French chemist Louis
Pasteur that the “germ theory of
disease” was proved.
Pasteur began by looking at the
alcohol fermentation process. He
discovered that sourness in wine
was caused by external agents—
microbes, or germs. A crisis in the
French silk industry, caused by an
epidemic among silkworms, then
allowed Pasteur to isolate and
identify the microorganisms that
caused the particular disease.IN CONTEXT
KEY FIGURE
Louis Pasteur (1822–95)BEFORE
1683 Dutch amateur scientist
Antonie van Leeuwenhoek
uses a microscope to observe
bacteria and protozoa.1796 Edward Jenner carries
out the first vaccination, using
the cowpox virus to protect
against smallpox.AFTER
1926 American microbiologist
Thomas Rivers distinguishes
between viruses and bacteria.1928 While studying
influenza, Scottish
bacteriologist Alexander
Fleming discovers penicillin.2007 An inventory of all
the microbes associated
with a healthy human body
is completed.IT IS THE MICROBES
THAT WILL HAVE THE
LAST WORD
MICROBIOLOGY
Microbes are the worker bees
that perform most of the
important functions
in your body.
Dr Robynne Chutkan,
Microbiome expert and authorUS_102-103_Microbiology.indd 102 12/11/18 6:24 PM