Taxonomic Diversity and Biotechnological Potential of Culturable Thermophilic Bacteria from Southwestern Algerian Hot Springs with Hydrogeochemical Water Analysis

Abstract Hot springs are exceptional natural ecosystems that host culturable thermophilic microorganisms with remarkable biotechnological potential. This study investigates the thermal water of the Ain Ouarka hot spring, located in Naama, southwestern Algeria. A comprehensive physicochemical characterization supported by hydrogeochemical analysis revealed that the Ain Ouarka thermal water belongs to the sulfate–chloride–calcic type, dominated by calcium and sulfate ions, as indicated by the Piper diagram. Thermophilic bacterial strains adapted to extreme environmental conditions were successfully isolated and characterized morphologically, biochemically, and molecularly. A total of 22 bacterial isolates exhibiting optimal growth at temperatures between 45 °C and 55 °C were obtained. Molecular identification based on 16S rDNA gene sequencing assigned these isolates to the phyla Firmicutes (55%), Betaproteobacteria (23%), Alphaproteobacteria (18%), and Actinobacteria (5%). The biotechnological relevance of these isolates was further demonstrated by their extracellular enzyme activities: 50% exhibited strong amylase activity, 9% showed protease activity, and 5% displayed lipase activity. Moreover, the antimicrobial potential of the isolates was evaluated, revealing significant inhibitory effects against Gram-positive and Gram-negative bacteria as well as Candida albicans. To the best of our knowledge, this study provides the first data of antimicrobial compound production by Pannonibacter phragmitetus EM12 and Chelativorans intermedius EM19. These findings highlight the Ain Ouarka hot spring as a valuable natural reservoir of resilient thermophilic bacteria possessing both enzymatic and antimicrobial properties, with promising applications in pharmaceutical and food industries