Phylogenetic Interrelationships of Round-Spore-Forming Bacilli Containing Cell Walls Based on Lysine and the Non-Spore-Forming Genera Caryophanon, Exiguobacterium, Kurthia, and Planococcus

The 16S rRNA gene sequences of "Bacillus aminovorans" and several species considered to be phylogenetically related to the group 2 bacilli of Ash et al. (C. Ash, J. A. E. Farrow, S. Wallbanks, and M. D. Collins, Lett. Appl. Microbiol. 13:202–206, 1991) were determined. A comparative analysis of the sequence data revealed that the round-spore-forming group 2 bacilli, together with some asporogenous taxa (the genera Caryophanon, Exiguobacterium, Kurthia, Planococcus), form a phylogenetically distinct cluster that is only remotely related to Bacillus subtilis, the type species of the genus Bacillus. Within this cluster, planococci, kurthiae, Caryophanon spp., and two lines defined by Bacillus sphaericus and Bacillus fusiformis and by Sporosarcina ureae, Bacillus pasteurii, Bacillus globisporus, and Bacillus psychrophilus were found to be distinct genera. Exiguobacterium aurantiacum and Brevibacterium acetylicum were found to form a distinct clade, which was peripherally related to this cluster. "B. aminovorans" exhibited no specific relationship with the group 2 bacilli or with any of the other reference species examined.