TAXONOMY AND PHYLOGENY OF INDUSTRIAL SOLVENT-PRODUCING CLOSTRIDIA

We performed a systematic study of 55 solvent-producing clostridial st rains, the majority of which are currently classified as Clostridium a cetobutylicum strains, by using a combination of biotyping and DNA fin gerprint analysis, The biotyping procedures used included rifampin sus ceptibility testing, bacteriocin typing, acid bacteriophage typing. Th e 55 strains examined exhibited a good correlation between their bioty pes and DNA fingerprints, which allowed us to divide them into nine gr oups, The DNA fingerprints of the nine groups differed markedly, but w ithin each group the DNA fingerprints exhibited a high level of simila rity. To determine the phylogenetic relationships of the nine groups, we performed a 16S rRNA gene sequence analysis. The results of a compa rative analysis of the partial sequence corresponding to positions 830 to 1383 (Escherichia coli numbering) of the 16S rRNA gene indicated t hat the nine biotype groups could be assembled into four taxonomic gro ups. The complete 16S rRNA sequences of strains representing these gro ups were determined. Our phylogenetic analysis revealed that the amylo lytic type strain C. acetobutylicum ATCC 824 (taxonomic group I) was o nly distantly related to the saccharolytic strains belonging to taxono mic groups II, III, and (levels of sequence similarity, 90 to 90.5%), The strains belonging to taxonomic groups II, III, and IV, represented by C. acetobutylicum NCP 262, ''Clostridium saccharoperbutylacetonicu m'' N1-4, and C. acetobutylicum NCIMB 8052(T) (T = type strain), respe ctively, were closely related (levels of sequence similarity, 98.2 to 98.9%). C. acetobutylicum NCIMB 8052(T) exhibited a level of similarit y of 100% with the type strain of Clostridium beijerinckii. Reclassifi cation of the saccharolytic solvent-producing strains is necessary, an d possible names for the four taxonomic groups are discussed.