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Characterization of the pyoluteorin biosynthetic gene cluster of Pseudomonas fluorescens Pf-5.

ABSTRACT: Ten genes (plt) required for the biosynthesis of pyoluteorin, an antifungal compound composed of a bichlorinated pyrrole linked to a resorcinol moiety, were identified within a 24-kb genomic region of Pseudomonas fluorescens Pf-5. The deduced amino acid sequences of eight plt genes were similar to the amino acid sequences of genes with known biosynthetic functions, including type I polyketide synthases (pltB, pltC), an acyl coenzyme A (acyl-CoA) dehydrogenase (pltE), an acyl-CoA synthetase (pltF), a thioesterase (pltG), and three halogenases (pltA, pltD, and pltM). Insertions of the transposon Tn5 or Tn3-nice or a kanamycin resistance gene in each of these genes abolished pyoluteorin production by Pf-5. The presumed functions of the eight plt products are consistent with biochemical transformations involved in pyoluteorin biosynthesis from proline and acetate precursors. Isotope labeling studies demonstrated that proline is the primary precursor to the dichloropyrrole moiety of pyoluteorin. The deduced amino acid sequence of the product of another plt gene, pltR, is similar to those of members of the LysR family of transcriptional activators. pltR and pltM are transcribed divergently from the pltLABCDEFG gene cluster, and a sequence with the characteristics of a LysR binding site was identified within the 486-bp intergenic region separating pltRM from pltLABCDEFG. Transcription of the pyoluteorin biosynthesis genes pltB, pltE, and pltF, assessed with transcriptional fusions to an ice nucleation reporter gene, was significantly greater in Pf-5 than in a pltR mutant of Pf-5. Therefore, PltR is proposed to be a transcriptional activator of linked pyoluteorin biosynthesis genes.

SUBMITTER: Nowak-Thompson B

PROVIDER: S-EPMC93630 | biostudies-literature | 1999 Apr

REPOSITORIES: biostudies-literature

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Characterization of the pyoluteorin biosynthetic gene cluster of Pseudomonas fluorescens Pf-5.

Nowak-Thompson B B Chaney N N Wing J S JS Gould S J SJ Loper J E JE

Journal of bacteriology 19990401 7

Ten genes (plt) required for the biosynthesis of pyoluteorin, an antifungal compound composed of a bichlorinated pyrrole linked to a resorcinol moiety, were identified within a 24-kb genomic region of Pseudomonas fluorescens Pf-5. The deduced amino acid sequences of eight plt genes were similar to the amino acid sequences of genes with known biosynthetic functions, including type I polyketide synthases (pltB, pltC), an acyl coenzyme A (acyl-CoA) dehydrogenase (pltE), an acyl-CoA synthetase (pltF ...[more]

PMID: 10094695

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Project description:BackgroundPseudomonas fluorescens Pf-5 is a plant-associated bacterium that inhabits the rhizosphere of a wide variety of plant species and and produces secondary metabolites suppressive of fungal and oomycete plant pathogens. The Pf-5 genome is rich in features consistent with its commensal lifestyle, and its sequence has revealed attributes associated with the strain's ability to compete and survive in the dynamic and microbiologically complex rhizosphere habitat. In this study, we analyzed mobile genetic elements of the Pf-5 genome in an effort to identify determinants that might contribute to Pf-5's ability to adapt to changing environmental conditions and/or colonize new ecological niches.ResultsSequence analyses revealed that the genome of Pf-5 is devoid of transposons and IS elements and that mobile genetic elements (MGEs) are represented by prophages and genomic islands that collectively span over 260 kb. The prophages include an F-pyocin-like prophage 01, a chimeric prophage 03, a lambdoid prophage 06, and decaying prophages 02, 04 and 05 with reduced size and/or complexity. The genomic islands are represented by a 115-kb integrative conjugative element (ICE) PFGI-1, which shares plasmid replication, recombination, and conjugative transfer genes with those from ICEs found in other Pseudomonas spp., and PFGI-2, which resembles a portion of pathogenicity islands in the genomes of the plant pathogens Pseudomonas syringae and P. viridiflava. Almost all of the MGEs in the Pf-5 genome are associated with phage-like integrase genes and are integrated into tRNA genes.ConclusionComparative analyses reveal that MGEs found in Pf-5 are subject to extensive recombination and have evolved in part via exchange of genetic material with other Pseudomonas spp. having commensal or pathogenic relationships with plants and animals. Although prophages and genomic islands from Pf-5 exhibit similarity to MGEs found in other Pseudomonas spp., they also carry a number of putative niche-specific genes that could affect the survival of P. fluorescens Pf-5 in natural habitats. Most notable are an approximately 35-kb segment of "cargo" genes in genomic island PFGI-1 and bacteriocin genes associated with prophages 1 and 4.

Dataset Information

Characterization of the pyoluteorin biosynthetic gene cluster of Pseudomonas fluorescens Pf-5.

Publications

Characterization of the pyoluteorin biosynthetic gene cluster of Pseudomonas fluorescens Pf-5.

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