Isolation, Antibacterial Screening, Phenotypic and Molecular Identification of Antimicrobial-producing Soil Streptomyces Strain

The increasing prevalence of antibiotic-resistant bacteria has prompted a global search for new antibiotics. Streptomycetaceae is one of the major families that produce antibiotics for medicinal use. Researchers have investigated the genus Streptomyces to identify new species that could produce potent antibacterial substances. This investigation was conducted to isolate and characterize Streptomyces strains with antibacterial potential from different soil samples in the AlKarak Governorate, Jordan. Soil samples were obtained from caves, home gardens, greenhouses, and agricultural farmlands in the Governorate. Streptomyces were isolated and identified from the various soil samples. The antibacterial activity of the Streptomyces isolates was examined against a group of test bacteria using primary (modified cross-streak method) and secondary (agar diffusion test) screening methods. The isolate with the highest antimicrobial activity was identified based on morphological, biochemical, and molecular characterization. The results indicated that twenty-four Streptomyces strains were isolated from the different soil samples, all showing antimicrobial potential against at least two of the test bacteria. One of the isolates, the C8 strain had the highest antimicrobial potential in the primary screening against all test bacteria and displayed activity in the secondary screening against four types of test bacterial strains. The sequence analysis of the 16S rDNA gene showed that isolate C8 was 98.7% similar to Streptomyces pratensiss. The present study's findings suggested that Streptomyces pratensiss strain C8 from cave soil could produce antibacterial compounds, perhaps supporting the search for naturally occurring bioactive medications.