Isolation and Characterization of Bacteria from the Gut of Bombyx mori that Degrade Cellulose, Xylan, Pectin and Starch and Their Impact on Digestion

Bombyx mori L. (Lepidoptera: Bombycidae) have been domesticated and widely used for silk production. It feeds on mulberry leaves. Mulberry leaves are mainly composed of pectin, xylan, cellulose and starch. Some of the digestive enzymes that degrade these carbohydrates might be produced by gut bacteria. Eleven isolates were obtained from the digestive tract of B. mori, including the Gram positive Bacillus circulans and Gram negative Proteus vulgaris, Klebsiella pneumoniae, Escherichia coli, Citrobacter freundii, Serratia liquefaciens, Enterobacter sp., Pseudomonas fluorescens, P. aeruginosa, Aeromonas sp., and Erwinia sp.. Three of these isolates, P. vulgaris, K. pneumoniae, C. freundii, were cellulolytic and xylanolytic, P. fluorescens and Erwinia sp., were pectinolytic and K. pneumoniae degraded starch. Aeromonas sp. was able to utilize the CMcellulose and xylan. S. liquefaciens was able to utilize three polysaccharides including CMcellulose, xylan and pectin. B. circulans was able to utilize all four polysaccharides with different efficacy. The gut of B. mori has an alkaline pH and all of the isolated bacterial strains were found to grow and degrade polysaccharides at alkaline pH. The number of cellulolytic bacteria increases with each instar

Pathogenicity, antibiotic susceptibility and genetic similarity of environmental and clinical isolates<i style=""> </i>of <i style="">Vibrio cholerae</i>

817-823Isolates of Vibrio cholerae were obtained from clinical and environmental samples and the pathogenicity of these isolates was confirmed by hemolytic assay. The clinical isolates were more pathogenic than environmental isolates. Antibiotic susceptibility of V. cholerae to a set of antibiotics showed a marked variation. The environmental isolates exhibited more resistance to the antibiotics than clinical isolates. The plasmid curing technique was used to check the encoding of antibiotic resistance gene in genome. In both isolates, the resistance to vancomycin and co-trimaxazole was not mediated by plasmid and it may probably be encoded in genome. RAPD method was adopted to find out the variation in the genome of the clinical isolates and environmental isolates of V. cholerae. The genomic similarity pattern revealed that the environmental Ogawa isolates were closely related to clinical Ogawa isolates. This study confirmed the existence of the complex nature of V. cholerae in its pathogenicity, response to a set of antibiotics and genetic similarity