The rapid increase of bacterial resistance strains to multiple antibiotics has become a global public health concern. In the present study, actinomycetes from different districts of Libyan soil were isolated and screened for their inhibitory activity against pathogenic bacteria and fungi. Three hundred soil samples were taken from 77 diverse ecosystems, including deserts, forests, pastureland, and cropland located in different climatic regions in Libya. A total of 164 actinomycetes were obtained. Of 164 isolates, 38 (23.2%) isolates were morphologically and microscopically characterized by spore chain and surface morphology, aerial and substrate mycelia and soluble pigments. The preliminary classification of the isolates illustrates that all isolates belong to the genus Streptomyces . These isolates were further examined for their antagonistic potential against nine pathogenic bacteria and fungi. Out of 38, 11 (28.9%) isolates showed their capability to produce inhibitory substances against at least two tested strains. Among bacterial strains, Staphylococcus aureus was susceptible to almost all eleven isolates (90.9%), while Streptococcus pyogenes was found to be resistant to most selected isolates (18.2%). The isolate, 063 (Wadan soil-desert zone) was the only isolate that exhibited broad spectrum antimicrobial activity against all tested pathogenic microbes, and hence was selected for further study. According to its cultural, morphological, physiological, and biochemical characteristics, the isolate 063 was identified as Streptomyces rochei . The results obtained indicate that the Libyan soil, particularly in extreme environments, could be a potent source of bioactive metabolites with antimicrobial potency against a wide variety of microbial pathogens. Thus, this investigation suggested that exploring new habitats in unexplored and untapped regions of Libya could provide a promising source of biologically active compounds for therapeutic applications.
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