Characterization of Antimicrobial Metabolites Produced by Halophilic Actinomyces Isolated from Aran-Bidgol and Maharloo lakes

One of the problems encountered in the treatment of infectious diseases today is the presence of antibiotic-resistant microorganisms. Therefore, the discovery of new sources for the production of biologically active compounds with antimicrobial properties can serve enormously in the treatment of infectious diseases and in the reduction of resistant multidrug-resistant microorganisms. The aim of this study was to determine and evaluate antimicrobial metabolites produced by salt-loving actinomycetes isolated from Aran, Bidgol and Maharloo lakes.

This descriptive cross-sectional study was done in1396 and 51 halophilic actinomyces were isolated from 115 sediment and water samples of Aran Bidgol and Maharloo Lakes. All isolates subjected to antimicrobial metabolite activity assay.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 athenticated 16S rRNA gene sequencing. Optimization of antimicrobial metabolite production was carried out by different temperatures, pHs, carbon nitrogen sources and the best phase of metabolite production and solvent for purification was dtertermined. Finally, possible structure of bioactive compounds was determined using UV-visible and mass spectrometry methods.

Out of 51strains of halophilic Actinomyces isolates, three strains indicated 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. Molecular identification of the antimicrobial metabolites producing strains recognized them as Streptomyces sp. Ahbb4, Streptomyces flavidofuscus strain HBUM1740 and Actinomycete Nd28. Optimal temperature and pH were 27°C, 8 respectively and the best C and N-sources were fructose, xylose and yeast extract and peptone. In addition, the best solvents for all bioactive compounds were methanol and xylene. The results obtained from UV-visible and GC mass spectrometry assay suggested the peptide nature of all compounds with chloroacetate, ethylcholoroacetate and 4 chloro 3 hydroxybutyronitrite groups.

According to the findings of the present study, new antimicrobial metabolites are produced by salt-loving actinomycetes, which require in vivo tests to be used for the treatment of infections, which should be included in other research.