DNA relatedness of Thermus strains, description of Thermus brockianus sp. nov., and proposal to reestablish Thermus thermophilus (Oshima and Imahori)

Aerobic, thermophilic, gram-negative bacteria obtained from Yellowstone National Park that were placed in the genus Thermus on the basis of phenotypic data were examined by chemotaxonomic techniques to determine their peptidoglycan compositions, their respiratory quinones, their mean DNA base compositions, and their levels of DNA-DNA homology as determined by both the filter hybridization and reassociation rate methods. These isolates from hot springs included Thermus aquaticus strains and strains of a new genospecies. We propose the name Thermus brockianus for this new genospecies; strain YS38 is the type strain of this taxon. A collection of 10 strains, including the type strain of "Thermus thermophilus", which were isolated from widely separated geothermal 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 reestablished, with strain HB8 as the type strain.