Objectives Bacillus spp. strain was screened and identified for eco-friendly biological control of plant pathogens, disease prevention and growth promotion.
Methods The antagonistic ability of the strain was determined by mycelial growth rate and detached leaves method, antimicrobial metabolites were determined by HPLC method, while plant hormones were assessed based on the basic biology and UPLC-MS. Based on the results of biolog system, multi-sequence phylogenic analysis and genome mining, the strain 19573-3 was identified, and the secondary metabolite gene clusters were analyzed.
Results Strain 19573-3 showed broad-spectrum antagonistic activity against Botrytis spp., Pythium spp., Phytophthora spp., Fusarium spp., etc. and had significant control efficiency on Bortrytis cinerea. Fengycin, salicylic acid, cytokinin and IAA were identified and quantitatively determined in the secondary metabolism of the strain. The production of cellulase, protease and siderophores were proved by selective medium plate. According to physiological and biochemical characteristics, the phylogenetic analysis of 16S rRNA and gyrA, and average nucleotide identity, strain 19573-3 was identified as Bacillus velezensis. B. velezensis 19573-3 had a single circular chromosome of 3,990,203 bp with a 46.56% G+C content, including 86 tRNA, 27 rRNA, and 8 sRNA. The bacterial genome contained 4146 genes that occupied 90.03% of the genome. Meanwhile, 13 secondary metabolite synthesis gene clusters were related to antagonism and growth promotion, which might encode the fengycin, surfactin, and bacillibactin.
Conclusions Strain 19573-3 is identified as B. velezensis. Good antagonistic effect was proved biologically and chemically as the determination of fengycin and plant hormones in the secondary metabolism extracts. Strain 19573-3 was composed of a circular chromosome of 3,990,203 bp in size, and the code clusters for producing fengycin, surfactin, and bacillibactin were predicted on it.
DownLoad: