History of Microbiology
the first insights
It wasnʼt always clear that
microscopic living
organisms exist. In the
1600ʼs a man named Anton
van Leeuwenhoek built his
own microscopes and made
the very first detailed
descriptions of microscopic
living creatures. He was
most likely observing single
celled eukarytoic microbes.
These little dots are
what bacteria look like
magnified a 1,000 times
under a microscope.
Leeuwenhoek later
described shapes like
these when examining
scrapings from human
teeth.
Leeuwenkoek examined pond water under his
microscopes and discovered a wonderful assortment of
living organisms like the example above.
In 1861, Louis Pasteur disproved the theory of
spontaneous generation by showing that nutrient
broth would only become cloudy with the growth of
bacteria if it was exposed to dust in the air carrying
already living bacteria. The bacteria did not simply
come into existence from nothing. He used swan
neck flasked which allowed air to enter the flask,
while the necks trapped dust and prevented it from
entering the nutrient broth.
Spontaneous Generation
For a long time, a debate took place
between scientists about the origin of
microbes and small animals like fruit flies.
Well into the 1800ʼs, many scientists and
philosophers believed that new microbes
originated from nothing in a process
called spontaneous generation.
The Germ Theory of Disease
Louis Pasteur also proposed one of the most
important ideas in microbiology. In 1857, he
proposed the Germ Theory of Disease which
hypothesized that several human diseases are
caued by bacteria or other microbes. Until this
time most people attributed disease to things
like spirits, “bad air” and even the faulty
character of the individual. This new
understanding that he provided had a
profound impact on the treatment of disease.
Louis Pasteur
Robert Koch, sometimes called the
“Father of Microbiology” contributed
several important tools and discoveries to
the study of bacteria. In 1876 he provided
strong evidence supporting the Germ
Theory of Disease by demonstrating that
Anthrax is caused by a bacteria called
Bacillus anthracis.
Robert Koch
Robert Koch also developed the first methods to grow bacteria in pure culture as colonies on potato slices. A colony is
a pure culture since it grows from a single cell and is composed of only one species. Later he developed the method of
using nutrient media solidified with gelatin to grow colonies. These methods, while rather simple, provided extremely
useful methods to begin studying different types of bacteria, thus launching the field of microbiology.
Mycobacterium tuberculosis and Kochʼs Postulates
In 1882 Robert Koch discovered the cause of Tuberculosis- a bacteria he called Mycobacterium tuberculosis. He
also proposed Kochʼs Postulates which was a 4 step methodology for determining that a specific bacteria causes a
specific disease. 1) The bacteria must be found in people with the disease. 2) The bacteria must be isolated and
grown in pure culture. 3) The bacteria must cause disease when introduced into a healthy individual (in animal
studies). 4) The bacteria must be re-isolated from the newly diseased individual. These steps provided a powerful
framework that quickly lead to the discovery of many other disease causing bacteria by other scientists.
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