Antibacterial Potential and Polyphasic Taxonomy of Streptomyces Isolates From Extreme Habitats.

OBJECTIVE: Within the scope of combating global antibacterial resistance, this study aimed to evaluate the biotechnological and antibacterial potentials of Streptomyces isolates retrieved from two distinct extreme habitats in the Eastern Anatolia Region of Türkiye through polyphasic characterization and secondary metabolite production optimization. METHODS: Soil physicochemical properties from extreme habitats were determined using potentiometric and conductometric methods, and Streptomyces isolates were retrieved via selective plating techniques. Following primary antibacterial screening using the cross-streak method, selected isolates underwent morphological, biochemical, and molecular characterization based on 16S rRNA, rpoB, and recA gene sequencing. Furthermore, the production of antibacterial metabolites by selected isolates was carried out by optimizing fermentation conditions to determine the most suitable culture media and cultivation periods. RESULTS: Among the isolates, 14.7% exhibited significant antibacterial activity. Polyphasic characterization identified three strategic isolates as Streptomyces rochei (BH011), Streptomyces bikiniensis (BH022), and Streptomyces inhibens (BH034), while BH006 and BH026 showed high phylogenetic similarity to Streptomyces ficellus and Streptomyces gobitricini, respectively. Fermentation optimization revealed GYM broth as the ideal medium for BH026, which demonstrated broad-spectrum activity, including a 25 mm inhibition zone against Escherichia coli. Conversely, isolate BH022 exhibited significantly enhanced antibacterial activity upon co-culture induction with Staphylococcus aureus. CONCLUSIONS: Our findings suggest that extreme environments in Türkiye represent significant hotspots for the identification potential biotechnological microbial sources. The enhancement of antibacterial activity through nutritional optimization and interspecies competition highlights the potential of these extreme-habitat isolates for further bioprospecting of bioactive secondary metabolites.