PHYLOGENETIC ANALYSIS OF THE GENUS DESULFOTOMACULUM - EVIDENCE FOR THE MISCLASSIFICATION OF DESULFOTOMACULUM-GUTTOIDEUM AND DESCRIPTION OF DESULFOTOMACULUM-ORIENTIS AS DESULFOSPOROSINUS-ORIENTIS GEN. NOV., COMB. NOV

Almost complete 16S ribosomal DNA (rDNA) sequences were determined for the type strains of nine species belonging to the genus Desulfotomacu lum and for seven strains described as strains of this genus. The sequ ences were compared with previously published 16S rDNA and rRNA sequen ces of the type strains or the other species of the genus. The majorit y of the species form a phylogenetically coherent cluster within the C lostridium-Bacillus subphylum nf gram-positive bacteria. The cluster c onsists of phylogenetically well-separated lineages containing (i) Des ulfotomaculum nigrificans, Desulfotomaculum aeronauticum, and Desulfot omaculum ruminis, (ii) Desulfotomaculum geothermicum, Desulfotomaculum thermosapovorans, and Desulfotomaculum sapomandens, (iii) Desulfotoma culum kuznetsovii, Desulfotomaculum australicum, and Desulfotomaculum thermocisternum, (iv) Desulfotomaculum thermobenzoicum and Desulfotoma culum thermoacetoxidans, and (v) Desulfotomaculum acetoxidans. Some as -yet-undescribed Desulfotomaculum strains are phylogenetically well-se parated from strains of the described species. Desulfotomaculum guttoi deum shares extremely high 16S rDNA similarity with certain Clostridiu m species (e.g., Clostridium sphenoides and Clostridium celerecrescens ) and is most likely a misidentified species. Desulfotomaculum orienti s represents a new genus which branches most closely to the genus Desu lfitobacterium. The name Desulfosporosinus orientis gen. nov., comb. n ov., is proposed for this taxon.