Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2005
Publication Date: 11/1/2005
Citation: Broadhagen, M., Paulsen, I., Loper, J.E. 2005. Reciprocal regulation of pyoluteorin production with membrane transporter gene expression in pseudomonas fluorescens pf-5. Applied and Environmental Microbiology. 71:6900-6909. Interpretive Summary: Pseudomonas fluorescens strain Pf-5 is a naturally-occurring bacterium that inhabits the surfaces of plant roots and functions as a biological control agent, protecting roots from infection by pathogens that live in the soil. Pf-5 produces many antibiotics that are toxic to seed- and root-rotting plant pathogens. Because these antibiotics are critical to the success of biological control, we study factors that influence antibiotic production by Pf-5. One of the antibiotics produced by Pf-5 is pyoluteorin, which is toxic against the plant pathogen Pythium ultimum. This paper describes a cluster of genes in the genome of Pf-5 that are involved in transport of the antibiotic pyoluteorin out of the bacterial cell. The study shows that regulation of pyoluteorin production is coordinated with regulation of pyoluteorin transport. The results contribute to an evolving understanding of factors influencing antibiotic production and biological control of plant disease by Pseudomonas fluorescens Pf-5.
Technical Abstract: Pyoluteorin is a chlorinated polyketide antibiotic secreted by the rhizosphere bacterium Pseudomonas fluorescens Pf-5. Genes encoding enzymes and transcriptional regulators involved in pyoluteorin production are clustered. Sequence analysis of genes adjacent to the known pyoluteorin biosynthetic gene cluster in Pf-5 revealed the presence of an ABC transporter system. We disrupted two putative ABC transporter genes with transcriptional fusions to an ice nucleation reporter gene. Mutations in pltI and pltJ, which are predicted to encode a membrane fusion protein and an ATP-binding cassette of the ABC transporter, respectively, greatly reduced pyoluteorin production by Pf-5. Conversely, transcription of pltI and pltJ was enhanced by exogenous pyoluteorin. These new observations parallel an earlier finding that pyoluteorin enhances transcription of pyoluteorin biosynthesis genes and pyoluteorin production in Pf-5. This report provides evidence for coordination of pyoluteorin production and transcription of genes encoding a linked transport apparatus, wherein each requires the other for optimal expression.