DNA RELATEDNESS OF THERMUS STRAINS, DESCRIPTION OF THERMUS-BROCKIANUSSP-NOV, AND PROPOSAL TO REESTABLISH THERMUS-THERMOPHILUS (OSHIMA AND IMAHORI)

Aerobic, thermophilic, gram-negative bacteria obtained from Yellowston e National Park that were placed in the genus Thermus on the basis of phenotypic data were examined by chemotaxonomic techniques to determin e their peptidoglycan compositions, their respiratory quinones, their mean DNA base compositions, and their levels of DNA-DNA homology as de termined by both the filter hybridization and reassociation rate metho ds. These isolates from hot springs included Thermus aquaticus strains and strains of a new genospecies. We propose the name Thermus brockia nus for this new genospecies; strain YS38 is the type strain of this t axon. A collection of 10 strains, including the type strain of ''Therm us thermophilus,'' which were isolated from widely separated geotherma l sites, exhibited high levels of DNA-DNA homology with each other and had similar physiological properties. Therefore, we propose that the species Thermus thermophilus (Oshima and imahori) should be reestablis hed, with strain HB8 as the type strain.