Myxobacteria restrain Phytophthora invasion by scavenging thiamine in soybean rhizosphere via outer membrane vesicle-secreted thiaminase I

Abstract

AbstractPublic metabolites such as vitamins play critical roles in maintaining the ecological functions of microbial community. However, the biochemical and physiological bases for fine-tuning of public metabolites in the microbiome remain poorly understood. Here, we examine the interactions between myxobacteria andPhytophthora sojae, an oomycete pathogen of soybean. We find that host plant and soil microbes complementP. sojae’s auxotrophy for thiamine. Whereas, myxobacteria inhibitsPhytophthoragrowth by a thiaminase I CcThi1 secreted into extracellular environment via outer membrane vesicles (OMVs). CcThi1 scavenges the required thiamine and thus arrests the thiamine sharing behavior ofP. sojaefrom the supplier, which interferes with amino acid metabolism and expression of pathogenic effectors, probably leading to impairment ofP. sojaegrowth and pathogenicity. Moreover, myxobacteria and CcThi1 are highly effective in regulating the thiamine levels in soil, which is correlated with the incidence of soybeanPhytophthoraroot rot. Our findings unravel a novel ecological tactic employed by myxobacteria to maintain the interspecific equilibrium in soil microbial community.