Chapter 9

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Jacquelyn G. Black
Microbiology: Principles and
Explorations
Sixth Edition
Chapter 9:
An Introduction to Taxonomy:
The Bacteria
Copyright © 2005 by John Wiley & Sons, Inc.
Carolus
Linnaeus
(1707-1778)
Taxonomy
• The science of classification
• Provides an orderly basis for the naming of
organisms
• Places organisms into a category or taxon
(plural: taxa)
• Carolus Linnaeus: 18th century Swedish
botanist; the Father of Taxonomy
Binomial Nomenclature
• The system used to name all living things
• The first name designates the genus (plural:
genera) and its first letter is capitalized
• The second name is the specific epithet, and it
is not capitalized
• Together the genus and specific epithet identify
the species
The Meaning of the Names of Some
Microorganisms
• Escherichia coli: Named after Theodore
Escherich in 1888; found in the colon
• Entamoeba histolytica: Ent, intestinal;
amoebae, shape/movement; histo, tissue; lytic,
lysing or digesting tissue
• Strain: A subgroup of a species with one or
more characteristics that distinguish it from
other members of the same species
Classification of Human Dog Wolf and a
Bacterium
Using a Taxonomic Key
• Dichotomous Key: A commonly used
key to identify organisms.
• Has paired statements describing
characteristics of organisms.
• Figure 9.4
Dichotomous Key for Classifying U.S.
Coins
Dichotomous
Key for
Classifying
Major
Bacterial
Groups
The Five Kingdom Classification
Some Typical Monerans
Archaeobacteria—
Extremophiles able to
exploit the unusual
habitat of a “black
smoker” vent
Some Typical Protists
Some Typical Fungi
Kingdom Animalia
Proposed Major Evolutionary Lines of
Descent
Theory About Three Domains
The Three Domains
• A new category even higher than
kingdom
• Archaea
• Bacteria
• Eukarya
The Three Domain System of
Classification
The Shrub of Life
Lateral Gene Transfer
Bacteria vs. Archaea
• Both have cell walls, however, archaea
lack peptidoglycan
• Bacteria have fatty acids present in their
membranes; archaea have isoprenes
• Bacteria lack histones ; archaea have
histone-like proteins associated with the
chromosome
Criteria for Classifying Bacteria
• Criteria for Classifying Bacteria
• Table 9.4
• Biochemical Tests for ID of Bacteria:
• Table 9.5
• Sugar fermentation
• Starch hydrolysis
• IMViC
Categories of Viruses
Stromatolite Mats
Fossil Stromatolite Cross Section
Filamentous Cyanobacteria-Paleolyngbya
Probable Evolutionary Tree Arrived at
by Numerical Taxonomy
DNA Sequencer
DNA Hybridization
Separation of
Proteins
Phage Typing
David H. Bergey
(1860-1937)
The Life Cycle of a Chlamydia
• Small, dark elementary bodies (EB) attach to a
host cell and enter by phagocytosis
• The EB, enclosed within a membrane-enclosed
vacuole, lose their thick walls and enlarge to
form reticulate bodies (RB)
• RB replicate and fill the cell
• RB condense to form infectious EB and are
released by lysis of the host cell
Chlamydia Life Cycle
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