lecture 1 intro to microbiology: history and taxonomy
TRANSCRIPT
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Lecture 1Intro to Microbiology: History
and Taxonomy
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Microbiology
• The study of organisms to small to be seen without a microscope
• Includes living microorganisms: bacteria, algae, fungi, protozoa
• AND non-cellular infectious agents: viruses, viroids, prions
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Why study Microorganisms?
• Microorganisms are the foundation for all life on earth
• They effect your everyday life
• Only a minority of microorganisms are pathogenic
• Microorganisms are found almost everywhere
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Microbes and Human Welfare
• Recycle chemical elements
• Decompose organic matter
• Bioremediation
• Biotechnology
• Gene therapy
• Genetic engineering
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Microbes can be used to clean up oil spills such as this one in Alaska
Courtesy of the Exxon Valdez Oil Spill Trustee Council/NOAA
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Microbes and Human Disease
• Everyone has microbes in and on body
• Person may or may not contract disease once they are in contact with it
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Infectious Disease
• Pathogens invade susceptible host
• Emerging infectious diseases
• Ebola
• BSE, Mad cow disease
• Know other emerging infectious diseases from book for exam
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Major Groups of the Microbial World1. Bacteria
2. Archeae
3. Fungi
4. Algae
5. Protozoans
6. Helminths
7. Viruses
8. Major Features9. Small size
10. Diverse appearance
11. Diverse genetics
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Bacteria
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Archaea
• Found in extreme environments
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Fungi
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Fungi
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Algae
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Protozoa
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Helminths
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Viruses
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The Spectrum of Microorganisms is Diverse
- There are over 10 million species of prokaryotes
- There are over 3600 known viruses- There are about 70,000 described species of
fungi
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Discovery of Microorganisms
• Robert Hooke published Micrographia (1665)
• Anton van Leeuwenhoek (1632-1723)
• He peered at a drop of lake water through a lens that he carefully ground
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Hooke’s Micrographia
© Library of Congress [LC-USZ62-95187]
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Cork cells
© Library of Congress [LC-USZ62-95187]
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Anton van Leeuwenhoek
Courtesy of Pfizer, Inc.
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Leeuwenhoek’s drawings of bacteria
Courtesy of Royal Society, London
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Next Question: Where did microorganisms originate?
• Spontaneous generation: Life originates from non-life, believed from the time of Aristotle (384-322 B.C.)
• Works of Redi, Pasteur, and Tyndall refute this theory
• Prove Germ Theory of Disease
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Francesco Redi (1626-1697)
• Proponents of spontaneous generation believed that worms in rotting meat came from meat itself
• Redi debunked this theory
• Experiments with meat
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New Experiments Needed to Refute Spontaneous Generation
• Typical Experiment: used nutrient broth (infusion): contains nutrients needed for microorganisms to grow
• 1. boil to kill all forms of life• 2. seal vessel• If cloudy after standing: spontaneous
generation• If clear: no spontaneous generation• Different investigators: Different results
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Louis Pasteur (1822-1894)
• Father of microbiology
• Demonstrated air is filled with microorganisms
• Demonstrated that sterile infusions will stay sterile in specially constructed flasks even when they were left open to the air
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John Tyndall
• Explained differences in results obtained from different laboratories
• Proved Pasteur correct
• He concluded that different infusions require different boiling times to be sterilized
• Because of heat resistant microorganisms: Endospores
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Endospores
• Some microorganisms exist in two forms: – 1. a cell that is readily killed by boiling– 2. one that is heat resistant
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Golden Age of Microbiology
• Rapid advances by Pasteur and Robert Koch
• Discovery of agents of many diseases and role of immunity in prevention and cure of disease
• Discoveries include:– Fermentation and pasteurization– Germ theory of disease– Vaccination
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Fermentation and Pasteurization
• Pasteur- why did wine sour?
• Believed at time, that converted sugars into alcohol
• Yeasts do the work of fermentation
• Bacteria cause spoilage
• Pasteurization
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Germ Theory of Disease
• Pasteur: to fight silkworm disease
• Ignaz Semmelweis: Instructed hospital staff to wash hands
• Lister: treated surgical wounds with phenol solution
• John Snow: Interviewed sick and healthy Londoners during cholera epidemic
• Robert Koch
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Ignaz Semmelweiss encouraged hospital staff to wash their hands
Courtesy of Pfizer, Inc.
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Robert Koch (1843-1910)
• Demonstrated that anthrax caused by Bacillus anthracis– Usual means of transmission: resistant endospores
• Introduced use of pure culture techniques for handling bacteria in lab
• Cultured bacteria on agar• Discovered Mycobacterium tuberculosis –
causative agent for tuberculosis• Proved germ theory of disease
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Vaccination
• Edward Jenner:
• Introduced vaccine for smallpox
• Inoculate with fluid from cowpox blisters prevented smallpox
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Modern developments in Microbiology
• Bacteriology
• Mycology
• Parasitology
• Immunology
• Virology
• Recombinant DNA technology
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Taxonomy
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Taxonomy
• Involves three steps:– 1. Identification– 2. Classification– 3. Nomenclature
Objective is to arrange organisms into categories that reflect the similarities of the individuals within the groups
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History
• Carolus Linnaeus: 1700’s: Two Kingdoms: Plants and Animals
• Ernst Haekel: 1866: Kingdom Protista
• R.H. Whittaker: 1969: Five Kingdoms
• Carl Woese: 1990: Three Domains
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Taxonomic Hierarchy
• Species: basic unit– Group of related species: strain
• Genus: group of similar species
• Family: group of similar genera, ends in - aceae• Order: group of similar families, ends in - ales• Class: group of similar orders, ends in - ia• Phylum: group of similar classes• Kingdom: group of similar Phyla• Domain: group of similar Kingdoms
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Domains of the Living World
• Bacteria
• Archaea
• Eucarya– Bacteria and Archaea look identical
– Also both are prokaryotes, however differ in chemical composition and are unrelated
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Eucarya
• All members of living world that are not prokaryotes are in domain eukarya
• May be single celled or multi-cellular
• Always contain true membrane-bound nucleus and other internal organelles
• Far more complex than prokaryotes
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Four Kingdoms within Domain Eukarya
• Animalia– Multicellular, heterotrophic
• Plantae– Multicellular, heterotrophic
• Protista: many single celled eukaryotes– Ex. Paramecium, algae, protozoa
• Fungi– Single celled: yeast– Multicellular: molds and mushrooms
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Bacteria
• Single-celled prokaryotes
• Most have specific shapes: cylindrical, spherical, and spiral
• Most have rigid cell walls
• Multiply by binary fission
• Many move using appendages
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Archaea
• Have same size, shape, and appearance as bacteria
• Multiply by binary fission and move primarily with flagella
• Also have cell walls, but differ from bacteria: no peptidoglycan
• Interesting Feature: able to grow in extreme environments
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Identification of Microorganisms
• Microscopic examination
• Culture characteristics
• Biochemical tests
• Nucleic Acid Analysis
• Serological Tests
• Person’s symptoms also play a role
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Classification of Microorganisms
• Phenotype: Physical appearance• Genotype: Genes
– Development of molecular techniques has made this possible
• Bergey’s Manual of Systematic Bacteriology– All known species described here– If properties of newly isolated organism do not
agree with any description, considered new organism
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Nomenclature
• International code for Nomenclature of Bacteria• Uses two-word naming system: Binomial
Nomenclature– First name is the Genus, capital– Second name is the species, lower case– Both are italicized– Example: Escherichia coli, or E.coli– Strains; minor differences with in species:
• E. coli strain B or E.coli strain K-12
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Nonliving Members of Microbial World
• In order to be considered alive, must be composed of one or more cells
• Viruses, Viroids, and prions are termed agents
• Viruses: – Piece of nucleic acid surrounded by protein
coat– Can only multiply inside human host cells– Obligate intercellular parasites
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Non-living members of the bacterial world
• Viroids:– Simpler than viruses– Single short piece of RNA– No protective coat– Can only multiply inside cells
• Prions:– Appear to only be protein without nucleic acid– Possible another agent is causing the disease
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