Screening of antibacterial producing actinomycetes from sediments of the Caspian Sea

Actinomycetes are interesting as a main producer of secondary metabolites and industrial antibiotics from marine environments. A total of 44 strains of actinomycetes were isolated from Caspian Sea sediments at a depth of 5-10 m. Preliminary screening was done using cross-streak method against 2 gram-positive and 4 gram-negative pathogen bacteria. The most potent strains MN2, MN3, MN38, MN39, MN40, MN41, and MN44 were used to extract the antibacterial substances. The antibacterial activities were performed using Kirby-Bauer disk diffusion method. Potent actinomycetes were screened for hydrolytic exoenzymatic activities (amylase and protease). All of the 24 isolates were active against at least to one of the test organisms. The MN38 strain showed activity against Staphylococcus aureus (20.0±0.5mm), Bacillus subtilis (27.0±0.2 mm), and Escherichia coli (20.0±0.3 mm). The MN39 strain was also active against E. coli (23.0±0.4mm), B. subtilis (23.0±0.2mm), Klebsiella pneumonia (24±0.1mm), whereas, the MN3 strain showed activity against Pseudomonas aeruginosa (20.0±0.2mm). The results of this investigation revealed that the marine actinomycetes of Caspian Sea sediments were potent source of novel antibiotics and bioactive compounds.