Geobacillus debilis sp. nov., a novel obligately thermophilic bacterium isolated from a cool soil environment, and reassignment of Bacillus pallidus to Geobacillus pallidus comb. nov.

Several aerobic, motile, rod-shaped, thermophilic, spore-forming Geobacillus bacteria predominantly giving a Gram-positive staining reaction were isolated from a cool soil environment in Northern Ireland and taxonomically investigated. Two isolates, F10 and Tf(T), showed low 16S rRNA gene sequence similarity to recognized members of the genus Geobacillus. Phylogenetic tree investigation using neighbour-joining, maximum-likelihood and parsimony methods indicated that strains F10 and Tf(T) represent a single novel species, for which the name Geobacillus debilis sp. nov. is proposed, with type strain Tf(T) (=DSM 16016(T)=NCIMB 13995(T)) and which belongs to a subgroup of the genus Geobacillus comprising Geobacillus toebii and Geobacillus caldoxylosilyticus. However, G. debilis showed closest affinities to Bacillus pallidus, which we propose should become Geobacillus pallidus comb. nov.