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.

Inducible nitric-oxide synthase (iNOS) has been implicated in many human diseases including insulin resistance. However, how iNOS causes or exacerbates insulin resistance remains largely unknown. Protein S-nitrosylation is now recognized as a prototype of a redox-dependent, cGMP-independent signaling component that mediates a variety of actions of nitric oxide (NO). Here we describe the mechanism of inactivation of Akt/protein kinase B (PKB) in NO donor-treated cells and diabetic (db/db) mice. NO donors induced S-nitrosylation and inactivation of Akt/PKB in vitro and in intact cells. The inhibitory effects of NO donor were independent of phosphatidylinositol 3-kinase and cGMP. In contrast, the concomitant presence of oxidative stress accelerated S-nitrosylation and inactivation of Akt/PKB. In vitro denitrosylation with reducing agent reactivated recombinant and cellular Akt/PKB from NO donortreated cells. Mutated Akt1/PKB␣ (C224S), in which cysteine 224 was substituted by serine, was resistant to NO donor-induced S-nitrosylation and inactivation, indicating that cysteine 224 is a major S-nitrosylation acceptor site. In addition, S-nitrosylation of Akt/PKB was increased in skeletal muscle of diabetic (db/db) mice compared with wild-type mice. These data suggest that Snitrosylation-mediated inactivation may contribute to the pathogenesis of iNOS-and/or oxidative stress-involved insulin resistance. Nitric oxide (NO)1 is an endogenous cell signaling molecule involved in the regulation of many physiological functions and in the mediation of a variety of pathophysiological processes. NO and NO-related compounds function as both protective and cytotoxic, dependent on the cellular context and the nature of the NO group. The multifaceted actions of the NO group can be classified into two categories: 1) authentic NO-mediated, cGMPdependent, and 2) reactive nitrogen species-mediated, cGMPindependent actions. Nitrosative post-translational modifications, including protein S-nitrosylation and tyrosine nitration, are involved in the cGMP-independent actions. The cGMP-dependent actions play critical roles in a variety of physiological processes, including NO-mediated vasodilation. In contrast, cGMP-independent, nitrosative protein modifications are postulated to be involved in the pathological responses (1-4).Nitric-oxide synthases (NOSs) consist of three distinct genes, inducible nitric-oxide synthase (iNOS), endothelial NOS (eNOS), and neuronal NOS (nNOS). NO is generated by iNOS to a much greater extent, to over 1,000-fold, compared with that produced by the constitutive NOSs, eNOS and nNOS (2, 5). iNOS and nitrosative stress have been implicated in many human diseases, including insulin resistance (6, 7), atherosclerosis (8), inflammation, and neurodegenerative disorders (9). This is largely based on the evidence that iNOS deficiency results in significant amelioration of, or resistance to, these diseases. However, little is known about the molecular mechanisms by which iNOS causes and/or exacerbates these diseases. Furthe...

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