Isolation and genome-wide analysis of Bacillus subtilis from Bactrian camels in Xinjiang

Abstract:

[Background] Three strains of Bacillus subtilis were isolated from camel milk and feces by the conventional culture method, and genome sequencing was performed for strain F10431 with strong probiotic effects in vitro. [Objective] To explore the probiotic potential, functional genes, and genetic basis of the isolates, so as to lay a theoretical foundation for the application and research of B. subtilis. [Methods] The enzyme production, stress tolerance, antimicrobial effect, and feeding safety of B. subtilis F10431, 2N2N, and 2N13N were evaluated in vitro. The second- and third-generation sequencing was performed for the whole genome and functional gene annotation of the isolates. [Results] The three strains of B. subtilis had tolerance to acids and bile salt, and strain F10431 had the strongest tolerance to intestinal and gastric fluids. All of the strains were capable of producing protease, amylase, cellulase, and antioxidant enzymes. Particularly, strain F10431 showed the protease activity of (3.17±0.26) nmol/(min·mL), the amylase activity of (0.48±0.04) nmol/(min·mL), the cellulase activity of (151.02±8.05) μg/(min·mL), and the superoxide dismutase activity of (1.81±0.31) μmol/(min·mL). The strains exerted strong inhibitory effects on Staphylococcus aureus and Escherichia coli and weak inhibitory effects on Salmonella. None of the strains produced hemolysis ring, thus being safe for feeding. [Conclusion] In this study, three camel-derived B. subtilis strains with excellent probiotic properties were isolated. F10431 with outstanding probiotic effects in vitro was sequenced, and the sequencing data were submitted to NCBI to obtain the GenBank accession number of MW721260. This study elucidated the functional mechanism and genomic characterization of F10431, providing theoretical support for the application of relevant probiotic preparations.