Novel mechanism of metabolic co-regulation coordinates the biosynthesis of secondary metabolites in <i>Pseudomonas protegens</i>.

Abstract

Metabolic co-regulation between biosynthetic pathways for secondary metabolites is common in microbes and can play an important role in microbial interactions. Here, we describe a novel mechanism of metabolic co-regulation in which an intermediate in one pathway is converted into signals that activate a second pathway. Our study focused on the co-regulation of 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin, two antimicrobial metabolites produced by the soil bacterium <i>Pseudomonas protegens</i>. We show that an intermediate in DAPG biosynthesis, phloroglucinol, is transformed by a halogenase encoded in the pyoluteorin gene cluster into mono- and di-chlorinated phloroglucinols. The chlorinated phloroglucinols function as intra- and inter-cellular signals that induce the expression of pyoluteorin biosynthetic genes, pyoluteorin production, and pyoluteorin-mediated inhibition of the plant-pathogenic bacterium <i>Erwinia amylovora</i>. This metabolic co-regulation provides a strategy for <i>P. protegens</i> to optimize the deployment of secondary metabolites with distinct roles in cooperative and competitive microbial interactions.