Antimicrobial Potential of Halotolerant Bacteria of the Genus Bacillus from Lake Solenoye (Lushnikovsky Reserve) and their Ability to Biosynthesize Surfactin

The species diversity and spectrum of antibiotic activity of 66 halotolerant bacilli isolated from the bottom sediments of the relict Lake Solenoe of the Lushnikovsky Nature Reserve of the Stavropol Territory were evaluated in relation to a number of phytopathogenic and conditionally pathogenic bacteria and fungi. The strains were represented by 8 species of the genus: Bacillus megaterium, B. pumilus, B. mojavensis, B. atrophaeus, B. cereus, B. thuringiensis, B. marisflavi, B.licheniformis and 4 strains belonged to the closely related taxa Paenibacillus glucanolyticus, P. elgi, Cytobacillus oceanisediminis and C. firmus. As a result of antimicrobial activity screening, 18 strains were selected that exhibit high or moderate (growth inhibition above 50%) antimicrobial activity against all phytopathogenic bacteria of the genus Pectobacterium, Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 25922. The ability to synthesize surfactins was evaluated, and strain differences were identified in different types of bacilli. As a result of the research, a potentially promising producer was selected: strains B. mojavensis 1sl and B. pumilus 37sl, with 126 and 134 mg/L of surfactin yields, respectively.