A polyphasic taxonomic study was performed on the type strain of Bacillus thermosphaericus DSM 10633T and three related soil isolates. On the basis of phenotypic characteristics, chemotaxonomic profiles and phylogenetic data a new genus, Ureibacillus gen. nov., is proposed for the strains in the Bacillus thermosphaericus cluster. Strains of this cluster fall into two DNA-DNA similarity groups: while one group contains the type strain of Ureibacillus thermosphaericus comb. nov. and a single soil isolate, the other contains two soil isolates. The two groups differed in the composition of isoprenoid quinones and some phenotypic properties. These data support the description of a novel species of Ureibacillus for which the name Ureibacillus terrenus is proposed. The type strain of this new species is TH9AT (= DSM 12654T = LMG 19470T).