Aims:  This study was conducted to clarify the taxonomic status of Bacteroides type A strains with high vitamin B12‐producing ability that is widely distributed in the intestinal tracts of freshwater fish. Methods and Results:  Seventeen strains of Bacteroides type A isolated from five fish species were all rod‐shaped and gram‐negative. The strains were positive for esculin hydrolysis, nitrate reduction, resistance to bile, acid phosphatase, and negative for the production of catalase and urease and the susceptibility to vancomycin. The G+C content of DNA from the 17 strains was 29·1–31·9 mol%, and 16S rDNA sequence analysis revealed a close phylogenetic relationship between Bacteroides type A strains and Cetobacterium somerae sharing 99·7–100% sequence similarity. In addition, strains were capable of producing vitamin B12 at a rate of 1·82–13·98 ng ml−1 in 48 h. Conclusion:  Phenotypic and phylogenetic characteristics indicated that all isolates previously classified as Bacteroides type A strains belong to C. someare. Significance and Impact of the Study:  This study provided the important finding of novel niche of vancomycin‐resistant bacteria such as C. somerae in the intestinal tract of freshwater fish.

KEY WORDS: coastal fish, culturability, direct count, fluorescent in situ hybridization method, intestinal bacteria, viable count.

Aims:  This study was undertaken to examine the properties of chitinases purified from Clostridium sp. E‐16, an intestinal bacterium of the South American sea lion (Otaria flavescens). We also elucidated the taxonomic status of this bacterium to better understand the role of intestinal anaerobic bacteria in marine animals. Methods and Results:  Two chitinases were purified with ammonium sulfate precipitation, affinity chromatography and preparative electrophoresis from culture supernatant fluid from Clostridium sp. E‐16. Molecular mass was estimated to be 77 kDa for chitinase 1 and 98 kDa for chitinase 2 by SDS‐PAGE. Optimum pH of both purified chitinases was between 5·0 and 7·0. Chitinase 1 was inhibited with Cu2+, Fe2+, Hg2+ and Zn2+, while chitinase 2 was inhibited with Fe2+. Phylogenetic analysis using 16S ribosomal DNA (rDNA) sequences and phenotypic characterization revealed that Clostridium sp. E‐16 was closely related to Clostridium baratii. Conclusions:  It is likely that chitinases from C. baratii or a C. baratii‐like bacterium play an important role in degradation of chitin in the intestinal tract of the South American sea lion and in marine environments. Significance and Impact of the Study:  This is the first report of chitinase purification and characterization from a marine Clostridium strain.