Characterization of a new Bacillus nakamurai soil isolate with strong antimicrobial and biocontrol potential

Since the last decades, the use of bacterial isolates to reduce or replace chemical pesticides has grown in importance. In that respect, the isolation of new promising plant-beneficial bacteria represents the first step to bring new efficient biocontrol products on the market. With that idea, several strains were isolated from soil samples collected from two different agro-ecological locations in Burundi. First, all these isolates were evaluated for their antimicrobial activities against a range of bacterial and fungal phytopathogens including species isolated from Burundian diseased crops. Among those beneficial isolates, the strain BDI-IS1 has been selected based on its highest antimicrobial potential. Indeed, this strain inhibited all the selected bacterial and fungal phytopathogens with similar efficacy as the commercialized strain B. velezensis QST713 (Serenade). Based on genome sequencing, this isolate has been classified as member of the poorly described Bacillus nakamurai species. Bioassays indicated that some soluble secondary metabolites produced by this strain are tightly involved in the antagonistic activities. Genome mining coupled with metabolomic studies revealed the diversity of structurally different compounds produced by this isolate, including dipeptides, non-ribosomally synthesized peptides and polyketides as well as ribosomally synthesized and post-translationally modified peptides. Understanding the involvement of each metabolite in the antimicrobial activities is being investigated, but these findings strongly suggest that this B. nakamurai BDI-IS1 strain can be considered as a good candidate in terms of biocontrol.