Isolation, Phenotypic Characterisation and Molecular Identification of Thermophilic and Halophilic Bacteria from the İzmir–Dikili (Bademli) Marine Hot Spring, Türkiye

In recent years, studies on extreme biodiversity have focused on biotechnologically important microorganisms resistant to extreme conditions such as high temperature, high salt, acid and pressure, together with their bioproducts. Hot springs are natural habitats for halophilic and thermophilic extremophiles. This study aimed to isolate and characterise thermophilic and halophilic bacteria from the İzmir/Dikili (Bademli) sea thermal spring, Turkey, and was carried out in three stages. In the first stage, samples (sea water, mud, sand) were collected from several stations of the Bademli Sea Spring and bacteria were isolated using Brown Broth and Thermus medium; microorganisms with different colony morphology were selected for phenotypic characterisation. In the second stage, strains with different morphological properties were coded and evaluated by physiological tests (motility, temperature, pH, oxygen), biochemical tests (starch and casein hydrolysis, catalase, citrate, urease, gelatine hydrolysis, oxidase), salt tolerance and antibiotic susceptibility, with results compared to reference strains. In the third stage, chromosomal DNA was isolated from selected strains and 16S rRNA analysis was performed using universal primers; sequences were compared by BLAST and aligned with homologous NCBI reference sequences using multiple sequence alignment. Phylogenetic trees were constructed in MEGA 7, with CLUSTAL W alignment and neighbor-joining distance matrices calculated under the Kimura two-parameter model. Twenty-seven strains with different colony and cell morphology were isolated, and 16S rRNA analysis showed these thermophilic and halophilic strains to be closely related to Bacillus and Anoxybacillus species.