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Chapter 1
The Evolution of
Microorganisms and
Microbiology

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The Importance of
Microorganisms
• most abundant group of organisms and are
found everywhere on the planet
• play a major role in recycling essential
elements
• source of nutrients and some carry out
photosynthesis
• benefit society by their production of food,
beverages, antibiotics and vitamins
• causative agents of some important diseases
– Refer to table: (Infectious Organisms in Nonhuman
Reservoirs that may be transmitted to humans)

3. Ojective Unit 1
• Associate selected pathogenic
microorganisms with specific
infectious diseases
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4. Fig. 33.8

5. Objective
• Define the science of microbiology
and describe some of the general
methods used in the study of
microorganisms
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What is Microbiology?
• generally defined as the study of
organisms too small to be clearly seen by
the unaided eye (i.e., microorganisms) &
the techniques used to study them.
• these organisms are relatively simple in
their construction and lack highly
differentiated cells and distinct tissues

7. Check out this website:
• http://learn.genetics.utah.edu/content/begin/cells/scale/
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8. Objective
• Describe very basic differences in
procaryotic and eucaryotic
morphology and the distribution of
microorganisms among the various
kingdoms or domains (Archaea,
Bacteria and Eucarya) in which
living organisms are categorized
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Members of the Microbial World
• Procaryotic cells lack a true
membrane-delimited nucleus
• Eucaryotic cells have a membrane-
enclosed nucleus, are more complex
morphologically and are usually
larger than procaryotic cells

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Classification Schemes
• five kingdom scheme includes Monera,
Protista, Fungi, Animalia and Plantae with
microbes placed in the first three kingdoms
• three domain alternative, based on a
comparison of ribosomal RNA, divides
microorganisms into Bacteria (true
bacteria), Archaea and Eucarya (eucaryotes)

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Figure 1.1
Carl Woese

12. The Microbial World
Bacteria Archaea Eucarya
Cell type Prokaryote Prokaryote Eukaryote
Cell
organization
Unicellular Unicellular Unicellular
or Multicellular
Cell Walls
(containing
peptidoglycan)
Yes No No
Membrane-
bond
organelles
No No Yes
Environments
Found in
All Extreme
environments
Not in extreme
12
1 2 3

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Domain Eucarya – all
eucaryotic
• animals, plants and eucaryotic
microorganisms
– microorganisms include protists
(unicellular algae, protozoa, slime
molds and water molds) and fungi
– most are larger than procaryotic cells

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Viruses
• acellular
• smallest of all microbes (smallest is
10,000 times smaller than a typical
bacterium)
• cause a range of diseases including
some cancers

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Discovery of Microorganisms
• Antony van
Leeuwenhoek (1632-
1723)
– first person to
observe and describe
microorganisms
accurately
Figure 1.3 (a)

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Figure 1.3 (b) and (c)

17. Objective
• Discuss & Describe the historical
concept of spontaneous generation
and the experiments that were
performed to disprove this
erroneous idea
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18. Objective
• Discuss
1.Francesco Redi (1626-1697)
2.John Needham (1713-1781) 1749
3.Lazzaro Spallanzani (1729-1799)
4.Louis Pasteur (1822-1895)
5.John Tyndall (1820-1893) &
Ferdinard Cohn (1828-1898)
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The Conflict over
Spontaneous Generation
• spontaneous generation
– living organisms can develop from
nonliving or decomposing matter

20. Francesco Redi (1626-1697)
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21. But Could Spontaneous Generation be
True for Microorganisms?
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22. John Needham (1713-1781) 1749
Lazzaro Spallanzani (1729-1799)
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Louis Pasteur (1822-1895)
• his experiments
– filtered air through cotton
– Placed in sterile broth
• results: microbial growth occurred

24. Louis Pasteur (1822-1895)
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Louis Pasteur (1822-1895)

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Final Blow to Theory of
Spontaneous Generation
• John Tyndall (1820-1893) & Ferdinard
Cohn (1828-1898)
– demonstrated that dust carries
microorganisms
– showed that if dust was absent, nutrient
broths remained sterile, even if directly
exposed to air
– also provided evidence for the existence of
exceptionally heat-resistant forms of
bacteria

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The Role of
Microorganisms in Disease
• was not immediately obvious
• establishing connection depended on
development of techniques for
studying microbes
• once established, led to study of host
defenses - immunology

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• Robert Koch (1843-1910)
– established the relationship between Bacillus
anthracis and anthrax
– used criteria developed by his teacher Jacob
Henle (1809-1895)
– these criteria now known as Koch’s
postulates
• still used today to establish the link between a
particular microorganism and a particular
disease

29. Objective
• Describe how Koch’s postulates are
used to establish the causal link
between a suspected microorganism
and a disease
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Koch’s Postulates

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The Development of
Techniques for Studying
Microbial Pathogens
• Koch’s work led to discovery or
development of:
– agar
– petri dish
– nutrient broth and nutrient agar
– methods for isolating microorganisms

32. Objective
• List the contributions made by the
following early pioneers in the
science of microbiology: Antony van
Leeuwenhoek, Redi, Pastuer,
Tyndall, Cohn, Koch, Lister, and
Carl Woese.
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Pasteur
• Pasteur and Roux
– discovered that incubation of cultures
for long intervals between transfers
caused pathogens to lose their ability to
cause disease
• Pasteur and his coworkers
– developed vaccines for chicken cholera,
anthrax, and rabies

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The Development of Industrial
Microbiology and Microbial
Ecology
• Louis Pasteur
– demonstrated that alcohol
fermentations and other fermentations
were the result of microbial activity
– developed the process of pasteurization
to preserve wine during storage

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– provided indirect evidence that
microorganisms were the causal agents of
disease
– developed a system of surgery designed to
prevent microorganisms from entering
wounds as well as methods for treating
instruments and surgical dressings
– his patients had fewer postoperative
infections
Joseph Lister