Microbiology: Principles and Explorations

Sixth Edition

Chapter 9:An Introduction to Taxonomy:

The Bacteria

Copyright © 2005 by John Wiley & Sons, Inc.

Jacquelyn G. Black

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