Actinomycetes for antimicrobial discovery isolated from mangrove soils in Malaysia

The mangrove ecosystem is known as a highly productive habitat for isolating actinomycetes which has the potential of producing biologically active secondary metabolites. However, this ecosystem is largely unexplored source for discovering actinomycetes. Therefore, eight different mangrove sites in Malaysia were randomly chosen to isolate and screen actinomycetes from soils sample. A total of 53 putative marine actinomycetes were isolated and it was found that 3% final concentration of sodium chloride (NaCl) was sufficient to support the growth of marine actinomycetes. Among the isolated filamentous bacteria, 5 isolates showed antimicrobial activity from direct culture broth against at least one of the test organism and 4 extracts of ethyl acetate showed activity against Gram positive test organisms using disc diffusion method. However, hexane extracts exhibited no antimicrobial activity. The antimicrobial activity was also screened by modified microtiter plate method using resazurin as an indicator and this modern technique helps in screening more samples with easy handling and provided faster results. The results revealed that marine actinomycete is a potential source to produce antibiotic.