EVIDENCE FOR THE PLACEMENT OF THE GRAM-NEGATIVE CATONELLA-MORBI (MOORE AND MOORE) AND JOHNSONELLA-IGNAVA (MOORE AND MOORE) WITHIN THE CLOSTRIDIUM SUBPHYLUM OF THE GRAM-POSITIVE BACTERIA ON THE BASIS OF 16S RIBOSOMAL-RNA SEQUENCES

Comparative 16S rRNA analysis was used to determine the phylogenetic p ositions of Catonella morbi and Johnsonella ignava, which are members of two monospecific genera of gram-negative anaerobic bacilli isolated from human gingival crevices. Both of these genera were found to belo ng to cluster XIVa (M. D. Collins, P. A. Lawson, A. Willems, J. J. Cor doba, J. Fernandez-Garayzabal, P. Garcia, J. Cai, H. Hippe, and J. A. E. Farrow, Int, J. Syst. Bacteriol, 44:812-826, 1994) of the Clostridi um subphylum of gram-positive bacteria. Within this cluster, which con tains several Clostridium, Coprococcus, Eubacterium, and Ruminococcus species, C. morbi and J. ignava formed two distinct lines that were se parate from all other taxa. Our findings support the separate generic status of the genera Catonella and Johnsonella and show that these gen era do not belong to the family Bacteroidaceae but instead belong to t he gram-positive Clostridium subphylum.