Siderophore-mediated interactions determine the disease suppressiveness of microbial consortia

Interactions between plant pathogens and root-associated microbes play an
important role in determining disease outcomes. While several studies have
suggested that steering these interactions may improve plant health, such
approaches have remained challenging in practice. Because of low iron
availability in most soils, competition for iron via secreted siderophore
molecules might influence microbial interaction outcomes.Here we tested if
bacterial interactions mediated by iron-scavenging
siderophores can be used to predict the disease suppressiveness
of microbial consortia against soil-borne Ralstonia solanacearum bacterial
pathogen in tomato rhizosphere. Iron availability significantly affected
the interactions within inoculated consortia and between the consortia and
the pathogen. We observed contrasting effects of siderophores and other
non-siderophore metabolites on the pathogen growth, while the siderophore
effects were relatively much stronger. Specifically, disease incidence was
reduced in vivo when the inoculated consortia produced siderophores that
the pathogen could not use for its own growth. Employing
siderophore-mediated interactions to engineer functionally robust
microbial inoculants show promise in protecting plants from soil-borne
pathogens.