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PHYLUM DEINOCOCCOBACTERIA

INTRODUCTION TO THE DEINOCOCCOBACTERIA

Members of this small, unique group are among the most resistant living things.  Deinococcus (Figure A) exhibits resistance to DNA damage by very high levels of radiation and mutagenic chemicals.  Thermus aquaticus, (Figure B) found in hot springs in Yellowstone National Park, is the source of the Taq DNA polymerase, the enzyme that makes the PCR reaction possible.  

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A. Deinococcus SEM micrograph in false color.

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B. Thermus taken with a phase-contrast microscope.
Images taken from:
A: http://www.oulu.fi/electronoptics/kuvat/galleria/piiri.jpg
B: http://biology.kenyon.edu/Microbial_Biorealm/bacteria/thermus/rightstrain.jpg

SYNOPTIC DESCRIPTION OF THE DEINOCOCCOBACTERIA

The following description comes mainly from Margulis and Schwartz (1998),  Brock et al. (1994), and Tudge (2000). 

I. SYNONYMS: Deinococci; Radiation-Resistant or Heat-Resistant Gram Positive Bacteria.

II. PHYLUM CHARACTERISTICS:

A. Structure

Cell Form: Cocci and rods.

Cell Wall: Gram positive; often complex with many layers; Peptidoglycan in wall uses ornithine for cross-linkage; although Gram-positive, it has an outer membrane; bright pink due to carotenoids.

Motility: Non-motile.

B. Physiology

O2 TOLERANCE: Aerobes.

Substrates: Deinococci utilize cytochromes and menaquinones in respiratory pathways.  Most metabolize sugars.

Products: Generally to water and CO2.

C. Other: Contain catalyase and an outer membrane that is not like that of the Gram negative bacteria.

D. Ecology: Free-living in hot springs.  Some have been found in the cooling water for nuclear reactors where the radiation dosage is thousands of times that of the lethal dosage for human beings.

SYSTEMATICS OF THE DEINOCOCCOBACTERIA

Margulis and Schwartz (1998) place these taxa together in a phylum that they designate B-13 (Deinococci).  Garrity et al. (2001 and 2003) also place them together in a phylum that they designate "Deinococcus-Thermus".

HIERARCHICAL CLASSIFICATION OF THE DEINOCOCCOBACTERIA

This system follows Margulis and Schwartz (1998) and Garrity et al. (2001 and 2003).
CLASS DEINOCOCCI

ORDER DEINOCOCCALES

Deinococcus.

ORDER THERMALES

Thermus, Meiothermus.

This page is maintained by Jack R. Holt.  Last revised: 03/17/2008 .