University of Isfahan Journal of Microbial Biology 3060-7647 14 53 2026 01 07 Screening and phylogenetic analysis of native halophilic Actinomycetes producing exopolysaccharide with antimicrobial activity Screening and phylogenetic analysis of native halophilic Actinomycetes producing exopolysaccharide with antimicrobial activity 31 48 29025 10.22108/bjm.2024.142099.1602 FA Laila Mosawi Department Of Microbiology, Faculty of Science, Qom Branch, Islamic Azad University, Qom, Iran. Seyyed Soheil Aghaei Department of icrobiology,Faculty science,Qom Branch,Islamic Azad University, Qom, Iran. Mohammad Reza Zand Monfared Department Of Microbiology, Faculty Science, Qom Branch, Islamic Azad University, Qom, Iran. Journal Article 2024 07 10 Exopolysaccharides (EPSs) play a crucial role in the resistance of microorganisms to various stresses, including salinity. The aim of this study was to screen the native halophilic strains of actinomycetes, which produce antimicrobial EPSs, isolated from the rhizosphere soils of Qom Salt Lake. Actinomycete isolates were obtained using ISP2 medium with different salt concentrations. A BHI liquid medium containing 2% sucrose was used for the preparation of EPS. The antimicrobial activity of the EPSs was evaluated using the agar well diffusion method, and the MIC and MBC values were determined using a 96-well microplate assay. The structure of the isolated EPS was analyzed by FTIR, HPLC and UV-Vis spectroscopy. In addition, their thermal properties and stability were evaluated by TGA. The selected isolates were identified on the basis of morphological, physiological and biochemical characteristics of EPS, as well as the 16S rRNA molecular method. A total of 30 native strains of halophilic actinomycetes were isolated in this study. Two of these isolates showed the ability to produce EPS with antimicrobial properties. The highest antimicrobial activity of EPS was observed against pathogenic strains at a concentration of 2% and a volume of 200 µl. FTIR results confirmed the presence of hydroxyl groups, while HPLC analysis showed that the heteropolysaccharide structure consisted of six monomers. UV-Vis analysis confirmed the presence of carboxyl, carbonyl, amine and ester functional groups. TGA showed acceptable thermal stability. Phylogenetic analysis of the isolates confirmed that the strain belonged to the genus Streptomyces with 100% similarity. The results of this study suggest that the native halophilic strain of Streptomyces isolated from the rhizosphere soils of Qom Salt Lake could serve as an important source for the production of EPS with various biotechnological applications, particularly in the food and pharmaceutical industries. Exopolysaccharides (EPSs) play a crucial role in the resistance of microorganisms to various stresses, including salinity. The aim of this study was to screen the native halophilic strains of actinomycetes, which produce antimicrobial EPSs, isolated from the rhizosphere soils of Qom Salt Lake. Actinomycete isolates were obtained using ISP2 medium with different salt concentrations. A BHI liquid medium containing 2% sucrose was used for the preparation of EPS. The antimicrobial activity of the EPSs was evaluated using the agar well diffusion method, and the MIC and MBC values were determined using a 96-well microplate assay. The structure of the isolated EPS was analyzed by FTIR, HPLC and UV-Vis spectroscopy. In addition, their thermal properties and stability were evaluated by TGA. The selected isolates were identified on the basis of morphological, physiological and biochemical characteristics of EPS, as well as the 16S rRNA molecular method. A total of 30 native strains of halophilic actinomycetes were isolated in this study. Two of these isolates showed the ability to produce EPS with antimicrobial properties. The highest antimicrobial activity of EPS was observed against pathogenic strains at a concentration of 2% and a volume of 200 µl. FTIR results confirmed the presence of hydroxyl groups, while HPLC analysis showed that the heteropolysaccharide structure consisted of six monomers. UV-Vis analysis confirmed the presence of carboxyl, carbonyl, amine and ester functional groups. TGA showed acceptable thermal stability. Phylogenetic analysis of the isolates confirmed that the strain belonged to the genus Streptomyces with 100% similarity. The results of this study suggest that the native halophilic strain of Streptomyces isolated from the rhizosphere soils of Qom Salt Lake could serve as an important source for the production of EPS with various biotechnological applications, particularly in the food and pharmaceutical industries.

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