Submitted to: Biology of Molecular Plant-Microbe Interactions
Publication Type: Book / Chapter
Publication Acceptance Date: 12/10/2007
Publication Date: 11/3/2008
Citation: Loper, J.E., Bruck, D.J., Pechy-Tarr, M., Maurhofer, M., Keel, C., Gross, H. 2008. Genomic Analysis of Secondary Metabolite Production by Pseudomonas fluorescens Pf-5. In: Lorito, M., Woo, S.L., Scala, F., editors. Biology of Molecular Plant-Microbe Interactions. Volume 6. [CD-ROM]. St. Paul, MN. International Society for Molecular Plant-Microbe Interactions. Chapter 101. Interpretive Summary:
Technical Abstract: The complete genomic sequences of several Pseudomonas spp. that live in a commensal relationship with plants are now available. Among these is the biological control bacterium Pseudomonas fluorescens Pf-5. Nearly 6% of the 7.07 Mb genome of Pf-5 is devoted to the biosynthesis of secondary metabolites, and most of the biosynthetic gene clusters are present in genomic islands that are not shared among other Pseudomonas spp. whose genomes have been sequenced to date. Most of the 1,472 genes unique to Pf-5, which lack orthologs in two other sequenced strains of P. fluorescens, are located in clusters. Twenty-eight of these clusters contain at least 10 genes unique to Pf-5, with the largest containing 69 unique genes. Three orphan gene clusters, which encode for the biosynthesis of unknown natural products, were identified in the genome of Pf-5. Natural products synthesized from two of these orphan gene clusters have now been identified. The novel cyclic lipopeptide, orfamide A, can lyse zoospores produced by phytopathogenic Phytophthora spp., and orfamide A production contributes to swarming motility of Pf-5. Several analogs of rhizoxin, an antifungal macrocyclic lactone with phytotoxic and antifungal activity, are synthesized from a large biosynthetic gene cluster in the Pf-5 genome. Linked to the rhizoxin biosynthetic locus is a cluster of genes encoding for an insect toxin related to Mcf (for “makes caterpillars floppy”) produced by Photorhabdus luminescens, an inhabitant of the gut of entomopathogenic nematodes. This gene cluster is also present in P. fluorescens strain CHA0, and its role in the insect toxicity exhibited by strain CHA0 and Pf-5 is under investigation. Pf-5 appears to have acquired a number of genomic islands, some of which contain secondary metabolite gene clusters that are likely to enhance its competitive fitness in the rhizosphere environment.