Isolation, identification and antimicrobial evaluation of marine actinomycetes from Oman sea sediments ‌

Abstract

Actinomycetes are gram positive and filamentous bacteria and produce major portion of the bioactive compounds hence play an integral role in the novel drugs development. Recent studies demonstrated that marine habitats inhabiting actinomycetes have unique biodiversity and metabolic activity. For the first time Oman Sea sediments were investigated as a source of antibiotic producing marine actinomycetes in this project. Approximately 84 isolates were obtained from 14 collected sediment samples. Among four culture media and two treatments, Glucose asparagine agar and heat treatment isolated 32 and 47 isolates respectively and exhibited highest efficiency. Evaluation of antimicrobial activity of the isolated actinomycetes by top layer agar revealed that 24, 12, 23 percent of isolates showed antimicrobial activity against S.aureus, E.coli and C.albicans respectively. Determination of Minimum inhibitory concentrations of extracted antibiotics were recorded as 128256, 128-512 and 62-128 µg/ml against S.aureus, E.coli and C.albicans respectively. Preliminary identification studies showed that the potent isolates exhibited typical morphology of Streptomyces genus predominantly. Result of Morphological, biochemical and chemotaxonomical identification revealed that IFSIRI 70 ، IFSIRI 137 ، IFSIRI 145، IFSIRI 193،IFSIRI 214 belonged to Streptomyces genus. Molecular identification by 16s rRNA gene analysis showed high similarity (99%) between IFSIRI 70 ، IFSIRI 137 ، IFSIRI 145، IFSIRI 193،IFSIRI 214 strains with S. chartreusis ، S. qinglanensis ، S. Cacaoi ، S. violaceoruber and S. diastaticus respectively. Phylogenetic analysis showed that isolated producer strains and some commercial antibiotic strains located in a common cluster. These results exhibited high antimicrobial potential of the potent actinomycetes isolates for new antibiotic discovery.