germ theory

1. The early Greeks believed that living things could
originate from nonliving matter (abiogenesis)
(the goddess Gea could create life from stones).
Aristotle discarded this notion, but he still held
that animals could arise spontaneously from
dissimilar organisms or from soil. (spontaneous
generation)
This concept was still felt as late as the 17th
century, but toward the end of that century a
several observations, experiments, and arguments
began that eventually refuted this concept.
History of Microbiology

2. In 1665, Robert Hooke (Englishman) reported that
living things were composed of little boxes or cells
using a microscope (was the first to use a
microscope to observe living things).
Antonie van Leeuwenhoek (1632–1723)
Microbiology essentially began with the
development of the microscope. Although others
may have seen microbes before him, Antonie van
Leeuwenhoek (1632–1723) was one of the first
people to observe microorganisms (1675) , using
a microscope of his own design.
(Dutch)
History of Microbiology

3. Chapter 1 The Microbial World and You
History of Microbiology
demonstrated that microorganisms are
present in the air.
Conditions Results
Nutrient broth placed
in flask, heated, not
sealed
Microbial growth
Nutrient broth placed
in flask, heated, then
sealed
No microbial growth
Spontaneous generation or biogenesis?
1861: Louis Pasteur (Father of medical bacteriology)

4. Chapter 1 The Microbial World and You
History of Microbiology
Next experiment, Pasteur’s S-shaped flask kept
microbes out but let air in. These experiments
form the basis of aseptic technique

5. Chapter 1 The Microbial World and You
History of Microbiology
The Golden Age of Microbiology
1857-1914
Beginning with Pasteur’s work, discoveries
included the relationship between microbes
and disease, immunity, and antimicrobial
drugs

6. Chapter 1 The Microbial World and You
History of Microbiology
Pasteur showed that microbes are
responsible for fermentation.
Fermentation is the conversion of sugar to
alcohol to make beer and wine.
Microbial growth is also responsible for
spoilage of food.
Bacteria that use alcohol and produce acetic
acid spoil wine by turning it to vinegar (acetic
acid).

7. Chapter 1 The Microbial World and You
History of Microbiology
Pasteur demonstrated that
these spoilage bacteria
could be killed by heat
(62.8 c) that was not hot
enough to evaporate the
alcohol in wine. This
application of a high heat
for a short time (30 mins) is
called pasteurization.

8. Contribution of Louis Pasteur
• He coined the term “ Microbiology”
• He disproved the Spontaneous generation Theory
• He demonstrated that anthrax was caused by
bacteria.
• He invented the process of pasteurization and
fermentation.
. The development of effective vaccine
(rabies and anthrax)
• Pasteur works along with subsequent
observations by Lister, Koch and others established
the germ theory of disease

9. Chapter 1 The Microbial World and You
History of Microbiology
The Germ Theory of Disease
1835: Agostino Bassi showed a silkworm
disease was caused by a fungus.
1865: Pasteur believed that another silkworm
disease was caused by a protozoan.
1840s: Ignaz Semmelwise Advocated
washing hands to stop the spread of
disease.

10. Chapter 1 The Microbial World and You
History of Microbiology
The Germ Theory of Disease
• 1860s: Joseph Lister used a chemical
disinfectant to prevent surgical wound
infections after looking at Pasteur’s work
showing microbes are in the air, can spoil
food, and cause animal diseases.

11. Chapter 1 The Microbial World and You
History of Microbiology
The Germ Theory of Disease
1876: Robert Koch provided proof that a
bacterium causes anthrax and provided the
experimental steps, Koch’s postulates, used
to prove that a specific microbe causes a
specific disease.
Koch was a physician and Pasteur’s young
rival

12. Chapter 1 The Microbial World and You
History of Microbiology
Koch's Postulates
are used to
prove the cause
of an infectious
disease.

13. Chapter 1 The Microbial World and You
History of Microbiology
Koch's Postulates
are a sequence
of experimental
steps to relate a
specific microbe
to a specific
disease.

14. 1892 Dmitri Iosifovich Ivanovski : Discovered
viruses

15. Chapter 1 The Microbial World and You
History of Microbiology
A young milkmaid informed the physician
Edward Jenner that she could not get
smallpox because she had already been
sick from cowpox.
1796: Edward Jenner inoculated a person
with cowpox virus. The person was then
protected from smallpox.
Called vaccination from vacca for cow
The protection is called immunity

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History of Microbiology
What can you say about the cowpox and
smallpox viruses?

17. Chapter 1 The Microbial World and You
History of Microbiology
Vaccinations
produced from avirulent microbial strains
produced from live viruses
produced from viral particles