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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)
Ojective Unit 1
• Associate selected pathogenic microorganisms with specific infectious diseases
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Fig. 33.8
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
Check out this website:• http://learn.genetics.utah.edu/content/begin/cells/scale/
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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
The Microbial WorldBacteria 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 extreme12
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)
Objective
• Discuss & Describe the historical concept of spontaneous generation and the experiments that were performed to disprove this erroneous idea
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Objective• Discuss1.Francesco Redi (1626-1697)2.John Needham (1713-1781) 17493.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
Francesco Redi (1626-1697)
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But Could Spontaneous Generation be True for Microorganisms?
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John Needham (1713-1781) 1749Lazzaro 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
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
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
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
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