Phylum ‘Deinococcus-Thermus’

 Phylum ‘Deinococcus–Thermus’*

Only three genera are included in this phylum, but two of these are of particular inter-est because of remarkable physiological properties. Thermus species are thermophiles whose best known member is T. aquaticus; this is the source of the thermostable en-zyme Taq polymerase, used in the polymerase chain reaction. Deinococcus species show an extraordinary degree of resistance to radiation, due, it seems, to an un-usually powerful DNA repair system. This also enables Deinococcus to resist chemical mutagens. Both Deinococcus and Thermus species have an unusual re-finement to the structure of their peptidoglycan, with ornithine replacing diaminopimelic acid (Figure 7.11).

Representative genera: Deinococcus, Thermus

The remaining phyla of Gram-negative bacteria are grouped together in Volume 5 of the second edition of Bergey.