Genomic insight into the salt tolerance and proteolytic activity of Bacillus subtilis

We assessed the salt tolerance and proteolytic activity of 40 genome-published Bacillus subtilis strains isolated from fermented Korean foods to illuminate the genomic background behind the functionality of B. subtilis in high-salt fermentation. On the basis of the salt tolerance and phenotypic proteolytic activity of the 40 strains, we selected five strains exhibiting different phenotypic characteristics. Comparative genomic analyses of these five strains provided genomic insight into the salt tolerance and proteolytic activity of B. subtilis. Two-component system (TCS) genes annotated as ybdGJK and laterally acquired authentic ATP-binding cassette (ABC) transporter system genes of tandem repeat structure might contribute to increase salt tolerance. The additional possession of gene homologs for CAAX protease family proteins and components of Clp (caseinolytic protease) complex, ATP-dependent Clp proteolytic subunit ClpP and AAA+ (ATPases associated with diverse cellular Activities) family ATPases, might determine the proteolytic activity of B. subtilis. This study established the scientific foundation for the viability and functionality of B. subtilis in high-salt fermentation. Two-component system and ABC transporter system can contribute to increase the salt tolerance of Bacillus subtilis; the gene homologs for CAAX protease family proteins and Clp complex may determine its proteolytic activity.