Chapter 1: An Invisible World - Los Angeles Mission College
Transcript of Chapter 1: An Invisible World - Los Angeles Mission College
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Chapter 1:
An Invisible World
2. A Systematic Approach
3. Types of Microorganisms
1. What Our Ancestors Knew
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1.1 – What Our Ancestors Knew
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Fermented Foods & Beverages
Evidence for fermented foods (e.g., yogurt, beer, wine, etc) dates
back as far as 7000 BC!
• the microbial basis (i.e., yeast and bacteria) was, of course, not known
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Health & Disease
Hippocrates (400 BC)
• Diseases have
natural causes
• First cause no harm
Thucydides (400 BC)
• Evidence-based
• plagues survivors
immune
Varro (36 BC)
• Proposed unseen
“minute creatures”
cause disease
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Anton van Leeuwenhoek (1673)
The first to observe microorganisms using his “magnifying lenses”.
• essentially began the
field of microbiology
• the importance of
microorganisms for
human welfare was not
appreciated until almost
200 years later!
The Discovery of Microorganisms
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Contributions of Louis Pasteur
2. disproved concept of spontaneous generation (1861)
• i.e., microbes do NOT arise from non-living material
1. Proposed “Germ Theory” of disease (1857)
3. Showed fermentation to be
carried out by microbes (1861)
4. Developed technique of
pasteurization to prevent food
and beverage spoilage
5. Developed several attenuated
vaccines
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Contributions of Robert KochIdentified the first bacterial pathogens:
Developed numerous advances in
microbiological techniques:
• simple staining methods
• fixation of specimens to slides
• pure culture techniques
• methods for counting microbes
• Bacillus anthracis (anthrax – 1876)
• Mycobacterium tuberculosis (tuberculosis – 1882)
• use of solid growth media
• accomplished by applying “Koch’s Postulates”
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1.2 – A Systematic Approach
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The Taxonomic Hierarchy
First proposed by Carolus Linnaeus in 1735.
*
*
* Added later
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Binomial Nomenclature
To avoid confusion, Linnaeus also proposed a way of
naming organisms that is still used today:
• every type of organism is referred by its genus name
followed by its specific epithet (i.e., species name)
Tyrannosaurus rex (T. rex) Escherichia coli (E. coli)
• names are Latin (or “Latinized” Greek) with the genus being a noun
and the specific epithet an adjective
• name should be in italics and only the genus is capitalized
which can also be abbreviated
**strain info can be listed after the specific epithet (e.g., E. coli O157:H7)**
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“Evolution” of the Tree of Life
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Modern Tree of Life
* *
* organisms
covered in
this course
*
(helminths)
Dinoflagellates
Carl Woese & George
Fox (1970s):
• discovered the
Archaea
• created the taxon
“Domain”
• based on rRNA
analysis
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1.3 – Types of Microorganisms
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Prokaryotes – Bacteria
• colonize all but the most extreme environments
• come in a variety of morphologies and arrangements
• chemically and metabolically very different from archaea…
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Prokaryotes – Archaea
• direct ancestors of all Eukaryotes
• not very well studied or understood
• many species
colonize very
harsh or extreme
environments
(e.g., high temp,
acid or salt)
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Eukaryotes - Protists
Protists are mostly single-celled eukaryotes:
Algae
photosynthetic protists (“plant-like”)
Diatoms
Protozoa
heterotrophic protists (“animal-like”)
Giardia lamblia
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Eukaryotes – Fungi
• all are eukaryotic heterotrophs with cell walls made of chitin
• unicellular (yeasts) or multicellular (molds, mushrooms)
Saccharomyces cerevisiae
Molds
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Eukaryotes – Helminths
Parasitic worms in the Animal Kingdom:
Flatworms (Platyhelminthes) Roundworms (Nematodes)
Taenia saginata (tapeworm) Dracunculus medinensis (Guinea worm)
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Viruses
Non-cellular, “non-living” pathogens consisting of a protein capsid
containing genetic material in the form of DNA or RNA.
Coronavirus Ebolavirus
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Key Terms for Chapter 1
• heterotroph
• helminth
• protozoa, algae
• archaea
• pathogen
• morphology, arrangement