Antimicrobial Activity of Bacillus velezensis K-9 Against Potato Scab and Its Genome-wide Analysis

Abstract

We isolated a bacterial strain K-9, identified as a species of the genus Bacillus, from a potato tuber sample. The inhibition rate of the strain K-9 against potato scab (Streptomyces scabies) was 44.90%. The whole genome sequence of Bacillus velezensis K-9 was obtained, and genomic analyses were performed. Complete genome sequence of strain K-9 was obtained through PacBio RSII and Illumina platforms. The size of genome is 3891530 bp, with estimated 3915 coding DNA sequences, GC content of 46.45%, 79 tRNA, and 10 rRNA. In addition, functional annotation of the strain K-9 genes was performed by GO, COG, KEGG, and CAZy analyses. There were 12 gene clusters for secondary metabolite synthesis in the genome of Bacillus velezensis K-9. Except for the unknown metabolites of the T3PKS (third polyketone), terpene and lanthipeptide class-II, the other eight gene clusters are associated with the synthesis of secondary metabolites that are common in Bacillus and have antibacterial activity. Based on the functional analysis of the genome, the lipopeptide extract and crude protein extract of the strain were verified as bacteriostatic. The metabolites of its antibacterial activity were analyzed and identified by metabolomics technology. The antibacterial protein-related substances such as polyketide synthetase, plastin synthetase, bacitin-biosynthetic protein and flagellin were isolated and identified from the crude protein extract. In the future, information derived from the thorough genomic analyses of this strain may be helpful in directed genetic modification of bacterial strains for production of antibacterial substances to control potato scab.