Isolation and Preliminary Characterization of Antimicrobial Agents from Marine Actinomycetes

Abstract

Microbial natural products are one of the major sources of novel drugs for pharmaceutical use; all evidences suggest that novel substances with therapeutic potential applications are still waiting to be discovered from their natural sources. Twenty actinomycete strains isolated from marine habitats were screened for their antimicrobial activities. Isolate (I-12) was found to be the best antimicrobial producer against the pathogenic tested organisms and it was chosen for further study. It was identified according to the macro and micro-morphological, physiological and biochemical characteristics of the isolates as member of genus Streptomyces sp. The nucleotide sequence of the 16S-rRNA gene of the most potent strains evidenced a 98% similarity with Streptomyces rochei. Optimization conditions for the maximum productivity of antimicrobial agent(s) were investigated and it showed that the maximum productivity was achieved at 28◦C, 7 days, pH 7-7.5 and agitation speed 180 rpm on starch nitrate medium. The chemical characterization of extracted antimicrobial agent(s) was partially identified by TLC, IR, GC-Mass chromatograph and NMR. It was suggested to be a methyl derivative of lankacidin antibiotic.