Plant Signaling Compounds Alter Secondary Metabolite Production Among Antagonistic Streptomyces

Streptomycetes have been implicated in the control of soil-borne plant pathogens, and are known to produce an extensive array of antimicrobial secondary metabolites. We investigated the hypothesis that plants manipulate the production of secondary metabolites by streptomycetes. We tested a collection of diverse Streptomyces isolates for responses to potential signaling molecules produced by plants, including plant hormones, flavonoids, sesquiterpene lactones, and crude root exudates. Secondary metabolite production was investigated with the use of high performance liquid chromatography (HPLC) and bioassays for inhibitory activity. We found evidence that streptomycetes respond to plant-produced compounds with altered patterns of secondary metabolite production. Streptomyces isolates in our study had the ability to chemically modify and produce close analogs of plant-derived compounds. The production of similar chemical compounds may facilitate cross-kingdom communication. Our work suggests the potential for plants to manipulate the activities of soil microbial communities, which may confer a selective advantage in suppression of plant pathogens. These results concur with studies from many different systems showing that microbial activity is tightly linked with the health and functioning of higher organisms.This work was supported by the USDA Microbial Observatories Program Grant 2006-35319-17445. Matthew Bakker is supported by an NSF Graduate Research Fellowship