MicrobiologyBytes: Introduction to Microbiology: Bacteria; Systematics Updated: January 19, 2005 Search

Prokaryotes:
Bacterial Genetic Systems

Taxonomy (The Science of Classification)

(a) Classification.

(b) Nomenclature.

(c) Identification.

The species concept and taxonomic ranks.

Hierarchical arrangement in classifications

Phenetic v phylogenetic classification.

Conventional Classification

Major characteristics used in conventional classification:

 

FEATURE:
Cell shape Cell wall constituents
Cell size Energy sources
Colonial morphology Fermentation products
Ultrastructural characteristics Growth temperature optimum & range
Staining behaviour Osmotic tolerance
Mechanism of motility Oxygen relationships
Cellular inclusions pH optimum & growth range
Carbon & nitrogen sources Sensitivity to metabolic inhibitors & antibiotics

Numerical taxonomy, the use of computers.

The similarity matrix and conversion to dendrogram (phenogram)

Selection of characters for identification purposes.

Summary of bacterial groups (From Bergey's Manual of Systematic Bacteriology):

Section: Example of Genus: Habitat:
Spirochaetes Treponema Parasites of animals
Microaerophilic Gram-negative curved rods Spirillum Aquatic, animal parasites
Aerobic Gram-negative rods Pseudomonas Soil, water, animal parasites
Facultatively Anaerobic Gram-negative rods Salmonella Intestinal tracts, animal parasites
Anaerobic Gram-negative rods Bacteroides Animal, insect parasites
Sulphate reducers Desulfovibrio Anoxic sediments
Anaerobic Gram-negative cocci Veillonella Animal intestines
Rickettsias, Chlamydias Rickettsia Arthropods, animal parasites (obligate intracellular)
Mycoplasma Mycoplasma Animal, plant parasites, no cell wall
Endosymbionts Holospora Symbionts of protozoans, insects, plants
Gram-positive cocci Staphylococcus Animal pathogens
Endospore formers Bacillus Soil, animal pathogens
Regular Gram-positive rods Lactobacillus Dairy products, animal intestines
Irregular Gram-positive rods Corynebacterium Soil, animal pathogens
Mycobacteria Mycobacterium Soil, plants, animal pathogens
Nocardioforms Nocardia Soil
Appendaged bacteria Caulobacter Aquatic, soil
Sheathed bacteria Sphaerotilus Aquatic
Sliding bacteria Cytophage Aquatic
Fruiting bacteria Myxococcus Soil
Aerobic lithotrophs Nitrobacter Soil, water
Archaeobacteria (archaea) Halobacterium Extreme environments
Anoxygenic phototrophs Chromatium Waters
Oxygenic phototrophs Anabaena Soil, water
Actinomycetes Streptomyces Soil

 

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Chemical and Molecular Approaches:

Genetic Elements in Prokaryotes:

Replication of Genetic Elements:

Exchange of Genetic Material:

CoverMicrobiology
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