Isolation of antagonistic marine bacteria from the surface of the gorgonian corals at Tuticorin, south east coast of India

Abstract

316-319Culturable heterotrophic bacteria present on the surface of two gorgonian corals, Subergorgia suberosa and Junceella juncea were isolated and the number of pigmented and non-pigmented strains was noted. The antagonistic effect of the marine isolates was tested against 8 human pathogens and 7 fish pathogens. It was observed that 82% (289) of the isolated bacterial strains were found to be non-pigmented and 61% (214) were identified as Gram-negative. Only 13% (46) of the isolated bacteria were found to be antagonistic against both human and fish pathogens. 74% (34) of the producer strains were found to be non-pigmented, however, mild antagonistic activity was found to be exhibited also by the pigmented strains. Percentage of Gram-negative strains showing activity was found to be 68% (145). All the indicator strains tested were inhibited by at least 10 of the antagonistic marine bacteria. A higher degree of inhibition was conferred by 3 of the isolates (G₁₁₀, G₁₁₁ and G₁₁₃) with maximum zones of inhibition against Escherichia coli (5.5mm) by the strain G₁₁₃. The strains showing higher degree of inhibition against human pathogens (G₁₁₀, G₁₁₁ and G₁₁₃) showed potent inhibition against the fish pathogens too with maximum inhibition against Proteus mirabilis (5mm) by the strain G₁₁₀. The symbiotic bacteria present on the surfaces of these gorgonian corals may yield novel metabolites