TOWARDS A PHYLOGENY OF THE CLOSTRIDIA BASED ON 16S RIBOSOMAL-RNA SEQUENCES

The 16S rRNA sequences of 17 species of the genus Clostridium were det ermined by direct sequencing of their PCR amplified genes. The sequenc es were aligned with those from other known clostridial species and re presentative low G + C Gram-positive relatives, and a phylogenetic tre e was constructed. It was evident from the comparative sequence analys is that the genus Clostridium as presently constituted is phylogenetic ally extremely heterogeneous. This study corroborates and extends earl ier findings in showing that many non-sporeforming bacteria are phylog enetically closely intermixed with Clostridium species. The taxonomic implications of the phylogenetic findings are discussed.