Potassium Phosphite Modulated the Soil Microbiome and Enriched the Antagonistic Bacteria Streptomyces Coelicoflavus and Paenibacillus Favisporus to Inhibit the Tomato Pathogen Ralstonia Solanacearum Synergistically

Abstract Background: Application of certain agricultural chemicals could modulate the soil microbiome and induce potential antagonistic microbes. However, the specific selective effects of agricultural chemicals on soil bacterial functions and their co-occurrences are not well understood, and no studies have verified that the enriched potential antagonistic microbes could enhance the antagonistic functions of the soil microbiome.Results: Here, the effects of potassium phosphite (KP), an environment-friendly agricultural chemical, on the soil bacterial composition, co-occurrences and antagonistic functions were determined, and the potential antagonistic bacteria against the tomato bacterial wilt pathogen Ralstonia solanacearum were isolated to test their functions and associations among these strains. Our results showed that application of KP enriched Bacillus, Paenibacillus and Streptomyces. The positive links among the OTUs belonging to these genera were increased, and positive associations between these OTUs and predicted genes related to antagonistic substance production were revealed. Two strains, Streptomyces coelicoflavus F13 and Paenibacillus favisporus Y7, were isolated, and they inhibited the growth of R. solanacearum. Genomic sequencing showed that both strains harboured streptomycin synthetic genes, and P. favisporus Y7 also contained surfactin synthetic gene cluster. Synergistic inhibition of R. solanacearum growth by P. favisporus Y7 and S. coelicoflavus F13 was observed in soil. Genome-scale metabolic modelling showed that dextrin and lactic acid were potential cross-feeding metabolites. In addition, the KP-modulated soil microbiome could suppress R. solanacearum growth. Conclusions: Our results highlight that a KP-modulated soil microbiome has considerable potential for biocontrol and indicate a new mechanism for the inhibition of R. solanacearum by KP-enriched soil bacteria.