Diversity and characteristics of alkalophilic proteolytic bacteria from Soda Lake Nukhe-Nur (Barguzinsky Basin, Buryatia)

Seven studied strains of proteolytic bacteria belonging to the phyla Pseudomonadota, Actinomycetota and Bacillota were isolated from water and bottom sediment samples of the Nukhe-Nur soda lake in the Barguzin depression. Determination of the ecophysiological properties of the cultures showed that the strains were alkaliphilic and alkalitolerant and developed at pH from 7.0 to 11.0 (optimum pH 7.5‒9.5). In relation to salinity, the isolated bacteria were mainly halotolerant. It was shown that the strains are capable of hydrolyzing p-nitroanilide substrates and exhibited maximum activity in hydrolysis of GlpAALpNA, BzRpNA and LpNA. It was established that peptidases are most active under alkaline conditions at pH 8.0–10.0 and are thermostable up to 50°C. The study of the activity of extracellular peptidases in different species of alkaliphilic bacteria allowed us to identify natural isolates with high enzymatic activity and different spectra of secreted extracellular peptidases, which, possibly, allows them to successfully use natural protein substrates in natural habitats.