Characterization of antimicrobial metabolites produced by halophilic Actinomyces isolated from Aran-Bidgol and Maharlu lakes

  Introduction: The purpose of this study was isolation of halophilic Actinomyces and the evaluation of their potential for producing antimicrobial metabolites. Material and method: To isolate antimicrobial metabolites producing Actinomyces, culture supernatant of 51 halophilic Actinnomyces isolates were assessed against Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, Candida albicans and Aspergillus niger using Well Diffusion Agar (WDA) method. Then the promising strains were identified by Api kit (bioMerieux) and 16S rRNA gene sequencing. The antimicrobial production was optimized at different temperatures, pHs, and variety of carbon, nitrogen-sources. Then the best solvents and the structural analysis of the metabolites carried out by UV-visible and GC mass spectrometry. Results: Out of 51strains of halophilic Actinomyces isolates, three strains showed potent activity for the production of antimicrobial metabolites. Bacillus cereus, Staphylococcus aureus and Candida albicans were sensitive to all and E. coli and pseudomonas aeruginosa were resistance to the bioactive compounds. Phenotyping and molecular identification of the antimicrobial metabolites producing strains recognized them as Streptomyces sp. Ahbb4, Streptomyces flavidofuscus strain HBUM1740 and Actinomycete Nd28. Optimal temperature, pH and C, N-sources for growth of these strains were 27°C, 8 and fructose, xylose and yeast extract and peptone respectively and the best solvents for all were methanol and xylene. In addition, The UV-visible and GC mass spectrometry suggesting the peptide nature of the compounds. However chloroacetate, ethylcholoroacetate and 4 chloro 3 hydroxybutyronitrite groups could be probably linked to the structures, but complete structure elucidations were not fully recognized. Discussion and conclusion: Our finding probably introduces new antimicrobial metabolites produced by halophilic Actinomyces however it needs more evaluation.