Halophilic Bacterial Diversity and Biotechnological Potential of the Gökçeada Salt Lake Lagoon (Çanakkale, Türkiye).

This study investigates the diversity, biochemical properties, and biotechnological potential of halophilic bacteria isolated from Gökçeada Salt Lake Lagoon (Çanakkale, Türkiye). Seasonal measurements of physicochemical parameters, including temperature, pH, dissolved oxygen (DO), and electrical conductivity (EC), revealed significant fluctuations likely driving microbial adaptation. A total of 27 bacterial isolates were obtained from water samples and characterized morphologically and biochemically. Molecular identification based on 16S rRNA gene sequencing revealed a diverse halophilic and halotolerant bacterial community. Phylogenetic analyses using Maximum Likelihood (ML) consistently grouped the isolates within dominant genera such as Bacillus, Halomonas, Marinococcus, Rhodobacter, and Exiguobacterium, which are known for their biotechnological relevance in enzyme production, and salt-adaptive metabolic activities in hypersaline environments. Antibiotic susceptibility testing, interpreted under the EUCAST v. 16.0 (2026) framework, showed significant resistance to Bacitracin (B10, 59.2%), Erythromycin (E15, 55.6%), and Ampicillin (AM10, 51.8%), while high susceptibility was recorded for Streptomycin (S10, 96.3%). The majority of isolates exhibited a Multiple Antibiotic Resistance (MAR) index ≥ 0.2, indicating exposure to environments under significant antimicrobial influence. Functional screening demonstrated frequent nitrogen fixation, phosphate solubilization, and indole-3-acetic acid (IAA) production, as well as notable heavy metal bioremediation potential. Six metabolically active and morphologically distinct strains were further analyzed for biotechnological applications, with the highest bacteriorhodopsin production recorded in Rhodobacter sp. (SW4) and the highest exopolysaccharide (EPS) yield observed in Exiguobacterium oxidotolerans (DW9). Overall, this study highlights the ecological significance of halophilic bacteria in hypersaline lagoons and underscores their promising applications in biotechnology.