In-vitro Antibacterial Activity of Coral Reef Associated Bacteria and Optimization of Bioactive Metabolite Production

This study reports the antibacterial activity of coral reef associated bacteria against bacterial pathogens and optimization of metabolite production. Twelve morphologically different bacterial were isolated from stony coral reef collected from Rameshwaram coastal area, Tamil Nadu. Cell free supernatant of all the bacterial isolates were tested against Staphylococcus aureus, Bacillus cereus, Salmonella typhi, Escherichia coli, and Klebsiella pneumoniae by agar well diffusion method. Of the 12 isolates tested, seven isolates showed antibacterial activity again at least one of the test organisms with the zone of inhibition in the range of 9-14 mm. The antibacterial compounds were extracted from the cell free supernatant using ethyl acetate and tested for antibacterial activity. In diffusion method, crude extract from strain RC12 showed 11-17 mm inhibition against all the test pathogens and the same was selected for optimization studies. Effect of culture conditions and medium components such as different carbon, nitrogen, mineral, pH, temperature on antibacterial metabolite production was studied by adopting one-factor-at-a- time method. The metabolite production was influenced by lactose, ammonium sulphate, K2HPO4 while the optimal cultivation conditions were pH 7 and 37°C. The potent strain RC12 was identified as Pseudomonas sp based on their phenotypic and biochemical characteristics. The finding of the present study concludes that coral reef bacteria found to be the best source for bioactive metabolites with broad spectrum activity.