the gyrB gene sequence similarities among them were 98.1–99.1 % (mean 98.7 %) (data not shown) and the sequence divergence between the B. subtilis subsp. subtilis and B. subtilis subsp. spizizenii strains was 5.0 %.Comparatively, the 16S rRNA gene-based tree yielded two clusters with a bootstrap value of 79 %: cluster 1 contained strains of B. subtilis, B. mojavensis, B. vallismortis, B.atrophaeus and B. amyloliquefaciens and cluster 2 contained strains of B. sonorensis and B. licheniformis. All Bacillus strains among these two cluster groups showed more than 99 % 16S rRNA gene sequence similarity, indicating that the gyrB gene is a better molecular marker than the 16S rRNA gene for the study of phylogenetic and taxonomic relationships at the species level in the B. subtilis group.