Antibacterial activity and mode of action of potassium tetraborate tetrahydrate against soft-rot bacterial plant pathogens.

Bacterial soft rot caused by the bacteria and is a destructive disease of vegetables, as well as ornamental plants. Several management options exist to help control these pathogens. Because of the limited success of these approaches, there is a need for the development of alternative methods to reduce losses. In this study, we evaluated the effect of potassium tetraborate tetrahydrate (PTB) on the growth of six and spp. Disc diffusion assays showed that spp. and spp. differ in their sensitivity to PTB. Spontaneous PTB-resistant mutants of were identified and further investigation of the mechanism of PTB resistance was conducted by full genome sequencing. Point mutations in genes and were found in a single PTB-resistant mutant. Additionally, point mutations in genes (synonym ) and were found in two independent PTB-resistant mutants. and encode peptide chain release factor 2 and its methyltransferase, respectively. We propose the disruption of translation activity due to PTB leads to growth inhibition. The PTB-resistant mutant showed altered swimming motility. Disease severity was reduced for -inoculated potato stems sprayed with PTB. We discuss the potential risk of selecting for bacterial resistance to this chemical.