Diversity and Characteristics of Alkaliphilic Proteolytic Bacteria from the Soda Lake Nukhe-Nur (Barguzin Depression, Buryatia)

Seven strains of proteolytic bacteria assigned to the phyla Pseudomonadota, Actinomycetota, and Bacillota were isolated from water and bottom sediment samples of the soda Lake Nukhe-Nur in the Barguzin Depression. Evaluation of the ecophysiological properties of the cultures showed that these strains were alkaliphilic and alkalitolerant and developed in the pH range from 7.0 to 11.0 (optimum pH, 7.5–9.5). With respect to salinity, the isolated bacteria were mainly halotolerant. The strains were capable of hydrolyzing p-nitroanilide substrates and showed maximum activity in the hydrolysis of GlpAALpNA, BzRpNA, and LpNA. Their peptidases were found to be most active under alkaline conditions at pH 8.0–10.0 and thermostable up to 50°C. Our study of extracellular peptidase activity in different species of alkaliphilic bacteria led to identification of natural isolates with high enzymatic activity and different spectra of secreted extracellular peptidases which probably allow them to successfully utilize available protein substrates in their natural habitats.