Isolation and molecular characterization of actinomycetes with antimicrobial and mosquito larvicidal properties

The present study aimed to isolate actinomycetes from soil samples collected from Western Ghats regions, Tamil Nadu, India. Totally 400 actinomycetes isolates were isolated, of which 161 (40.2%) showed antimicrobial activity in preliminary screening. Secondary screening yielded 27 active isolates; twelve of them showed good antimicrobial and larvicidal activities. Five isolates namely S12-4, S12-17, S12-8, DPS-14 and FMS-20 presented 98%, 93%, 87%, 82%, and 80% larvicidal activity against Cx. quinquefasciatus; very low larvicidal activity was observed against Ae. aegypti. S12-4 showed 100% larval mortality against An. stephensi. RAPD results showed highest similarity between DPS-122 and KFS-24 (0.89246). The polymorphic index observed in the primers ranged from 0.286 (OPA-09) to 0.07 (OPC-18). The results suggest that Western Ghats regions may be a good natural source for isolation of actinobacteria and thereby for discovering novel molecules with antimicrobial and mosquito larvicidal properties.