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

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

Antibacterial activity of the winged oyster Pteria chinensis (Pterioida: Pteridae)

369-372The whole body extracts of the winged oyster, Pteria chinensis obtained with different solvents were assayed for antibacterial activity using agar well diffusion technique against human and fish pathogens. The acetone and chloroform crude extracts exhibited broad antibacterial activity. Highest activity was exhibited against Klebsiella pneumoniae (5 mm) and Staphylococcus epidermidis (5 mm) by the crude extract of acetone and against Salmonella paratyphi B (5 mm) by the chloroform extract. Similarly, the crude extract of chloroform was found to inhibit 8 out of 10 fish pathogens tested. The column-purified acetone fractions showed higher activity against Klebsiella pneumoniae (5 mm), Sreptococcus pneumoniae (4 mm), Serratia marcescens (4 mm) and Proteus mirabilis (4 mm). The MIC of the 100% acetone fraction was found to be lower for the pathogens, S. marcescens (100 μg) and P. mirabilis (150 μg) and hence 100% acetonated fraction of the extract of P. chinensis can be considered as potent antimicrobial compound against these pathogens