Isolation and screening of soil microorganisms for membrane-active antimicrobial metabolites

The focus of this study was antimicrobial membrane-activity of microorganisms isolated from soils of Iran. In this work soil samples were collected from desert and farming zones of Northern and Central of Iran. A total number of 75 species consist of 36 bacteria, 28 fungi and 11 actinomycetes were isolated from the soil samples. In the primary screening that was performed to evaluate antimicrobial activity, isolated microorganisms were analyzed in terms of their general inhibition effects to indicator strains E. coli, C. albicans, and S. cervisiae. It has been found that 23 isolates including 4 bacteria, 13 fungi and 6 actinomycetes, were effective against test microorganisms. In the secondary screening to determine membrane-active metabolites producing microorganisms, isolates which had an inhibitory effect against test microorganisms, were analyzed for membrane activity using a Rapid Chromatic Detection method. Based on color and fluorescence changes that are easily identified by the naked eye and fluorescent microscope, 3 species consist of 1 fungus and 2 actinomycetes had membrane-activity effect and were stored for the sake of further study and identification.