Genomic characterization and probiotic potency of Bacillus velezensis CPA1-1 reveals its potential for aquaculture applications

Biological prevention and control are increasingly applied in sustainable aquaculture, and Bacillus spp. has been revealed to good alternatives to antibiotics. This research examined the probiotic capabilities of Bacillus velezensis CPA1-1 by genomic and phenotypic analysis. The genome sequence showed that B. velezensis CPA1-1 has a 3,925,520 bp chromosome with 46.49 % GC content and 3762 CDSs. And eight clusters of secondary metabolite biosynthesis genes related to antibacterial compounds were predicted in CPA1-1 genome, including surfactin, difficidin, bacillibactin, fengycin, bacilysin, bacillaene, macrolactin H, butirosin A. Besides, the antimicrobial assay indicated that strain CPA1-1 exhibited strong antagonistic capacity against non-O1/O139 Vibrio cholerae GXFL1-4 isolated from diseased Macrobrachium rosenbergii, and MIC of CPA1-1 fermentation broth against GXFL1-4 was 1.0 × 105 CFU/mL. Furthermore, administering CPA1-1 markedly elevated the activities of ACP, AKP, and SOD in M. rosenbergii, and the immune-related genes, including ALF, Crustin, Hemocyanin, Prophenoloxidase, C-type lectin and HSP70, also exhibited higher expression in the CPA1-1 treated groups. Additionally, M. rosenbergii in the test group treated with CPA1-1 could resist non-O1/O139 V. cholerae GXFL1-4 infection by the challenge test. Our study contributed to reveal biocontrol mechanisms of B. velezensis CPA1-1, and demonstrated that CPA1-1 has promise as a probiotic agent for aquaculture. •Genome analysis of Bacillus velezensis CPA1-1 revealed a large number of gene clusters involved in antimicrobial synthesis.•B. velezensis CPA1-1 enhanced immune responses and disease resistance of host.•B. velezensis CPA1-1 possesses prominent probiotic properties.