THE PHYLOGENY OF THE GENUS CLOSTRIDIUM - PROPOSAL OF 5 NEW GENERA AND11 NEW SPECIES COMBINATIONS

The 16S rRNA gene sequences of 34 named and unnamed clostridial strain s were determined by PCR direct sequencing and were compared with more than 80 previously determined clostridial sequences and the previousl y published sequences of representative species of other low- G+C-cont ent gram-positive genera, thereby providing an almost complete picture of the genealogical interrelationships of the clostridia. The results of our phylogenetic analysis corroborate and extend previous findings in showing that the genus Clostridium is extremely heterogeneous, wit h many species phylogenetically intermixed with other spore-forming an d non-spore-forming genera. The genus Clostridium is clearly in need o f major revision, and the rRNA structures defined in this and previous studies may provide a sound basis for future taxonomic restructuring. The problems and different possibilities for restructuring are discus sed in light of the phenotypic and phylogenetic data, and a possible h ierarchical structure for the clostridia and their close relatives is presented. On the basis of phenotypic criteria and the results of phyl ogenetic analyses the following five new genera and 11 new combination s are proposed: Caloramator gen. nov., with Caloramator fervidus comb. nov.; Filifactor gen. nov., with Filifactor villosus comb. nov.; Moor ella gen, nov., with Moorella thermoacetica comb. nov. and Moorella th ermoautotrophica comb. nov.; Oxobacter gen. nov., with Oxobacter pfenn igii comb. nov.; Oxalophagus gen. nov., with Oxalophagus oxalicus comb . nov.; Eubacterium barkeri comb. nov.; Paenibacillus durum comb. nov. ; Thermoanaerobacter kivui comb. nov.; Thermoanaerobacter thermocopria e comb, nov.; and Thermoanerobacterium thermosaccharolyticum comb. nov .