Isolation and Characterization of Gut Micro Biota from Some Estuarine Fishes

Gut flora has a continuous and dynamic effect on the host's gut and systemic immune systems. The gut microbiota of fish has been studied extensively using various techniques; little information is available on the correlation between gut microbiota and host activity. In the present investigation three species of estuarine fishes were taken with regard to their microbial population in the gut region and enzymatic analysis of those gut isolates. The total heterotrophic bacterial load ranged from 0.8x106 to 4.5x106 CFU/g of gut sample and it was found to be the maximum of 4.5x106 CFU/g in Oreochromis mossambicus gut followed by 3.1x106 CFU/g in Oreochromis leucostictus gut and minimum of 0.8x106 CFU/g in Etroplus suratenis. The isolates were identified by various biochemical tests. Pseudomonas, Vibrio and Bacilli are the common bacteria found in all three fishes. The bacterial isolates were subjected to quantitative estimation of enzymes viz., amylase, lipase and protease. Varied kinds of results were obtained in different fish species. However it was observed that 20% of the isolates produced only amylase. A collection of 10 bacterial isolates from three fishes were screened for antagonistic activity against human and fish bacterial pathogens. Upon testing all these strains, it became apparent that strains isolated from the fish O.mossambicus, exhibited antimicrobial activity against Klebsiella pneumoniae (17mm) and Vibrio cholerae (12mm). Thus the present preliminary study showed the variation in the gut micro-flora of different fish species and the microbes from marine environment may be useful in development of probiotics, drugs and also in the industrial enzyme production.