Novel ecological niche of Cetobacterium somerae, an anaerobic bacterium in the intestinal tracts of freshwater fish.
OBJECTIVE
This study was conducted to clarify the taxonomic status of Bacteroides type A strains with high vitamin B(12)-producing ability that is widely distributed in the intestinal tracts of freshwater fish.


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 x 1-31 x 9 mol%, and 16S rDNA sequence analysis revealed a close phylogenetic relationship between Bacteroides type A strains and Cetobacterium somerae sharing 99 x 7-100% sequence similarity. In addition, strains were capable of producing vitamin B(12) at a rate of 1 x 82-13 x 98 ng ml(-1) in 48 h.


CONCLUSIONS
Phenotypic and phylogenetic characteristics indicated that all isolates previously classified as Bacteroides type A strains belong to C. someare.


CONCLUSIONS
This study provided the important finding of novel niche of vancomycin-resistant bacteria such as C. somerae in the intestinal tract of freshwater fish.
Tsuchiya
C
C
Department of Marine Science and Resources, Nihon University, Kameino, Fujisawa, Kanagawa, Japan.
Sakata
T
T
Sugita
H
H
D000818:Animals; D001439:Bacteroides / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001482:Base Composition; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D005399:Fishes / Q000382:microbiology*; D005618:Fresh Water; D045182:Fusobacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007422:Intestines / Q000382:microbiology*; D007564:Japan; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D014805:Vitamin B 12 / Q000096:biosynthesis
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D014805:Vitamin B 12