| Abstrakt: |
In the present study, ten crab samples Portunus sanguinolentus (Three spotted crab) from Mudasalodai landing centre were collected and aerobic forms of gut bacteria were isolated. These crab species are commonly available in Mudasalodai landing center. The TVC (total bacterial count) of Portunus sanguinolentus gut sample were ranged from 2.6×105 to 3.1×105. In the present work, a total of 9 different bacterial species were detected in the gut of the selected crab. The observed aerobic bacterial populations in the gut of Portunus sanguinolentusi and their percentages of occurrences were Bacillus (7.5%), E. coli (20%), Vibrio spp. (25%), Staphylococcus aureus (12.5%), Salmonella spp. (10%), Pseudomonas (12.5%), Klebsiella spp. (7.5%), Listeria spp. (2.5%) and Shigella ssp. (2.5%) were the bacterial flora observed and they were identified using standard biochemical methods. In the present study, the observed antibacterial activities against different Fish pathogens such as Aeromonas hydrophila (2.3 cm), Vibrio vulnificus (2.5cm), Falvobacterium columnare (3.1 cm), Vibrio ordalii (2.3 cm). The isolates were screened for their antibacterial activity against a panel of human bacterial pathogens. The results showed, among the different crab gut bacterial isolates, the Pseudomonas isolate showed highest activity against the wide range of human and fish pathogens. Hence it was further identified using 16S rRNA based molecular identification. The strain was identified as Pseudomonas stutzeri. The potential antimicrobial compound producing Pseudomonas stutzeri isolate was further optimized for different physicochemical growth parameters using broth medium. Various parameters on growth of P. stutzeri SJ3 isolate showed 36 h incubation (2.22 OD), 160 rpm agitation (1.72 OD), pH 7 (1.81 OD), 37oC (1.75 OD), 2.5% salinity (1.8 OD), 2% glucose as carbon source (1.98 OD) and 1.5% yeast extract as nitrogen source (1.93 OD) as the ideal conditions. Growth in the mass cultivation medium under optimized conditions at the end of 36 h of incubation was 3.42 OD with the antimicrobial activity zone of 3.9 mm. In the present study, the antimicrobial compound production was found to be growth dependent. Hence, the Pseudomonas stutzeri isolated from the gut of the Portunus sanguinolentus was a potential candidate for the production of antimicrobial compound against the fish bacterial pathogens. [ABSTRACT FROM AUTHOR] |
