Identification and whole-genome sequencing of a bacterial strain isolated from healthy rice plants antagonistic to Magnaporthe oryzae

Rice blast is a globally devastating fungal disease that affects the production of rice (Oryza sativa), and the screening of excellent biocontrol strains is an important direction for the biological control of the fungus that causes rice blast disease (Magnaporthe oryzae).The objectives were to obtain strains that were highly antagonistic to rice blast, analyze the genetic information of the antagonistic bacterium YN-917, and explore the resources of its antagonistic gene cluster. The antagonistic bacteria were isolated and identified by the plate confrontation method, morphological observation, physiological and biochemical identification, and molecular biology methods. In addition, the strains were subjected to whole-genome sequencing, and their sequences were analyzed. Strain YN-917 was screened from healthy rice plants of the variety Xiangzaoxian 24, which is susceptible to rice blast, and it inhibited M. oryzae by 72.63% ± 1.30%. Additionally, the strain had different degrees of inhibitory effects on various plant pathogenic fungi and was highly resistant to stress. The morphological observation, analysis of physiological and biochemical features, 16S rRNA homology analysis, and whole-genome sequencing analysis revealed that the strain YN-917 was Bacillus cereus (GenBank No.: PRJNA687285). The total length of its whole genome was 5326162 bp, and its average G + C content was 35.37%. It was composed of one circular chromosome and one endoplasmic plasmid. There were 5483 genes encoded on average. They included 105 tRNA genes, 42 self-replicating RNA (sRNA), 178 tandem repeat sequences, three prophages, and nine genomic islands. The prediction of antagonistic gene cluster demonstrated that the genome sequence of YN-917 had six secondary metabolic gene biosynthetic clusters, including those for bacteriocins, siderophores, non-ribosomal peptide synthetases (NRPs), and terpene. This study provides a theoretical basis to further explore microbial resources and their metabolic gene clusters for agricultural biological control.