Taxonomic revision of the genus
Geobacillus
: emendation of
Geobacillus
,
G. stearothermophilus
,
G. jurassicus
,
G. toebii
,
G. thermodenitrificans
and G. thermoglucosidans (nom. corrig., formerly ‘thermoglucosidasius’); transfer of
Bacillus thermantarcticus
to the genus as G. thermantarcticus comb. nov.; proposal of Caldibacillus debilis gen. nov., comb. nov.; transfer of
G. tepidamans
to
Anoxybacillus
as A. tepidamans comb. nov.; and proposal of Anoxybacillus caldiproteolyticus sp. nov.
Sixty-two strains of thermophilic aerobic endospore-forming bacteria were subjected to polyphasic taxonomic study including 16S rRNA gene sequence analysis, polar lipid and fatty acid analysis, phenotypic characterization, and DNA–DNA hybridization experiments. Distinct clusters of the species Geobacillus stearothermophilus , Geobacillus thermodenitrificans , Geobacillus toebii and Geobacillus thermoglucosidasius were formed, allowing their descriptions to be emended, and the distinctiveness of the poorly represented species Geobacillus jurassicus , Geobacillus subterraneus and Geobacillus caldoxylosilyticus was confirmed. It is proposed that the name Geobacillus thermoglucosidasius be corrected to Geobacillus thermoglucosidans nom. corrig. Bacillus thermantarcticus clustered between Geobacillus species on the basis of 16S rRNA gene sequence analysis, and its transfer to the genus Geobacillus as Geobacillus thermantarcticus comb. nov. (type strain LMG 23032T = DSM 9572T = strain M1T = R-35644T) is proposed. The above-mentioned species, together with Geobacillus thermoleovorans and Geobacillus thermocatenulatus , form a monophyletic cluster representing the genus Geobacillus . The distinctiveness of ‘Geobacillus caldoproteolyticus’ was confirmed and it is proposed that it be accommodated, along with Geobacillus tepidamans , in the genus Anoxybacillus as Anoxybacillus caldiproteolyticus sp. nov. (type strain DSM 15730T = ATCC BAA-818T = LMG 26209T = R-35652T) and Anoxybacillus tepidamans comb. nov. (type strain LMG 26208T = ATCC BAA-942T = DSM 16325T = R-35643T), respectively. The type strain of Geobacillus debilis was not closely related to any members of the genera Anoxybacillus and Geobacillus , and it is proposed that this species be placed in the new genus Caldibacillus as Caldibacillus debilis gen. nov. comb. nov. The type strain of the type species, Caldibacillus debilis, is LMG 23386T ( = DSM 16016T = NCIMB 13995T = TfT = R-35653T).