Antibacterial Activity of Actinobacteria Isolated from Mangroves of Andaman and Nicobar Islands, India

Mangrove environment supports a rich and diverse group of microorganisms. These bacteria perform various ecologically important activities in these ecosystems like nitrogen fixation, methanogenesis etc. and also by the release of various kinds of compounds in the environment. In the present study, sediment samples from the three zones of mangrove ecosystems viz. proximal, middle and distal were examined for Actinobacteria. A total of 23 Actinobacterial colonies were isolated. The THBC varied between 24 + 0.82 X 106 in Proximal Zone to 50 + 1.7 x 106 in the distal zone in Burmanallah with an increasing trend in the THBC from proximal to the distal zone. While in Carbyn’s Cove, THBC ranged between 20 + 2.16 x 106 in the middle zone and 42 + 1.7 x 106 in the distal zone. An increase in the TAC towards sea was obtained in TAC from Nil in the distal zone to 4 + 1.7 X 106 in the proximal zone in Burmanallah and in Carbyn’s Cove, TAC ranged between 0.0006 + 0.0001 X 106 in the distal zone and 8 + 0.47 X 106 in the proximal zone. ANOSIM (R: 0.932) have shown that microbial community structure was not different between sites and zones at a significance level of 1.7% . This also confirmed the similarity seen in the MDS. The diversity is high in the proximal stations and in the distal zone of Carbyn’s Cove. The Actinobacteria viz. Micromonospora sp., Streptomyces aburaviensis, Streptomyces aurantiogriesius, Streptomyces aurofasciculus, Streptomyces flavoviridis and Nocardia astreoides. S. aurantiogriesius have shown the maximum activity with more than 10 mm zone of inhibition against Klebseilla sp., E. coli, V. cholera and S. flexheri. While S. aburaviensis have shown high activity against Klebseilla sp., E. coli and V. cholera. The other Streptomyces species like S. aurofasciculus and S. flavoviridis have shown medium activity against the pathogens. The present study could be drawn that marine environment yields a greater number of isolates per source that is comparable with that obtained from mangrove soils. On the other side, the number of isolates obtained from mangrove sediments is lower, particularly in the case of Actinobacteria. The present study also shows that the two study area Barmanallha and Carbyn’s Cove) of south Andaman have high potential Actinobacteria with bioactivity useful for identification of some novel compounds in future.