History of
Microbiology
JAHS Microbiology 2015
Life on Earth
Ancestors of bacteria were the first inhabitants
of Earth.
● Earliest evidence of life comes from 3.5
billion year old sedimentary rocks from
Western Australia and Greenland
● May have chemosynthesized from outputs of
hydrothermal vents
○ Miller-Urey experiments
The Cell Theory
In 1838, scientists Matthais Schleiden and
Theodor Schwann were the main contributors
to the cell theory.
● All living things are made of one or more
cells.
● All cells come from preexisting cells.
● The cell is the basic unit of life.
Discovery of Microbes
The first microbes were observed in
1673 by Anton van Leeuwenhoek, a
Dutch scientist.
● Using a handcrafted microscope,
Leeuwenhoek was the first to view
and describe single-celled organisms
which he called “animalcules”
The Debate Over Spontaneous Generation
The hypothesis that living organisms arise from
nonliving matter is called spontaneous
generation. According to spontaneous
generation, a “vital force” forms life.
● The alternative hypothesis, that the living
organisms arise from preexisting life, is
called biogenesis.
Evidence
1668: Francisco Redi filled six jars with
decaying meat.
Conditions
Results
Three jars covered with
fine net
No maggots
Three open jars
Maggots appeared
Evidence
1745: John Needham, Roman Catholic Priest,
put boiled broth into covered flasks.
Conditions
Nutrient Broth heated,
then placed in sealed
flask
Results
Microbial Growth
Evidence
1765: Lazzaro Spallanazi boiled nutrient
solutions in flasks.
Conditions
Nutrient Broth placed in
flask, heated, then
sealed
Results
No Microbial Growth
Evidence
1861: Louis Pasteur demonstrated that
microbes are present in air.
Conditions
Results
Nutrient broth placed in flask, heated, No Microbial Growth
not sealed – flask remains upright
Nutrient broth placed in flask, heated, Microbial Growth
no sealed – flask tilted
Pasteur
Pasteur’s S-shaped flask kept microbes out but
let air in.
The Golden Age of Microbiology: 1857-1914
Beginning with Pasteur’s work, discoveries
included the relationship between microbes and
disease, immunity, and antimicrobial drugs.
Fermentation and Pasteurization
Louis Pasteur showed that microbes are
responsible for fermentation.
● Microbial growth is responsible for spoilage of food.
● Bacteria that use alcohol and produce acetic acid spoil
wine by turning it to vinegar (acetic acid).
○ Pasteur demonstrated that these spoilage bacteria
could be killed by heat that was not hot enough to
evaporate the alcohol in wine.
The Germ Theory of Disease
● 1860s: Joseph Lister used a chemical
disinfectant to prevent surgical wound
infections after looking at Pasteur’s work.
● 1876: Robert Koch proved that a bacterium
causes anthrax and provided the
experimental steps, Koch’s postulates, to
prove that a specific microbe causes a
specific disease.
Koch’s Postulates
● The microorganism must be found in abundance in all
organisms suffering from the disease, but should not be
found in healthy organisms.
● The microorganism must be isolated from a diseased
organism and grown in pure culture.
● The cultured microorganism should cause disease
when introduced into a healthy organism.
● The microorganism must be reisolated from the
inoculated, diseased experimental host and identified as
being identical to the original specific causative agent.