Phylogenetic relationships of three amino-acid-utilizing anaerobes, Selenomonas acidaminovorans, 'Selenomonas acidaminophila' and Eubacterium acidaminophilum, as inferred from partial 16S rDNA nucleotide sequences and proposal of Thermanaerovibrio acidaminovorans gen. nov., comb. nov and Anaeromusaacidaminophila gen. nov., comb. nov.

16S rRNA gene sequences of three previously described amino-acid-fermenting anaerobes, Selenomonas acidaminovorans, 'Selenomonas acidaminophila' and E ubacterium acidaminophilum, were determined. All three were found to cluste r within the Clostridium and related genera of the subphylum of the Gram-po sitive bacteria. The thermophile, S. acidaminovorans, formed an individual line of descent and was equidistantly placed between Dethiosulfovibrio pept idovorans and Anaerobaculum thermoterrenum (similarity of 85%), both of whi ch also form single lines of descent. 'S. acidaminophila' was related to Cl ostridium quercicolum, a member of cluster IX, with a similarity of 90%, wh ereas E. acidaminophilum was closely related to Clostridium litorale (simil arity of 96%) as a member of cluster XI. Based on the phylogenetic data pre sented in this report and the phenotypic descriptions of these bacteria pub lished previously, it is recommended that S. acidaminovorans be transferred to a new genus, Thermanaerovibrio gen. nov., as Thermanaerovibrio acidamin ovorans comb. nov. and 'Selenomonas acidaminophila' be transferred to it ne w genus, Anaeromusa gen, nov., as Anaeromusa acidaminophila comb, nov. Thou gh the transfer of E. acidaminophilum to a new taxon is justified, this is not recommended until the taxonomic status of all the members of cluster XI has been reviewed.