title: Evidence and characterization of a gene cluster required for the production of viscosin, a lipopeptide biosurfactant, by a strain of Pseudomonas fluorescens.
abstract: The genetic control of viscosin production was examined in a strain of Pseudomonas fluorescens (PfA7B) that causes broccoli head rot. Viscosin is a potent lipopeptide biosurfactant that enables the bacteria to come into intimate contact with the difficult-to-wet waxy heads of broccoli. Tn5 mutagenesis completely disrupted viscosin production as shown by HPLC analysis of the mutagenized cell lysates. The Vis- mutants retained their pectolytic capability and were able to decay potato slices. On broccoli, however, the Vis- mutants caused decay of wounded florets, but the decay failed to spread to adjacent nonwounded florets as had occurred with the wild-type PfA7B. Triparental matings of the Vis- mutants with their corresponding wild-type clones and the helper Escherichia coli HB101 carrying the mobilization plasmid pPK2013 resulted in three stable viscosin-producing transconjugants that caused typical decay of broccoli tissue. Linkage maps of clones and protein profiles showed that a 25-kb chromosomal DNA region of PfA7B affected the production of three high molecular mass proteins required for viscosin synthesis. These proteins, approximately 218, 215, and 137 kDa in size, likely compose a synthetase complex that assembles the nine amino acid peptide of viscosin and subsequently attaches this to the hydrophobic fatty acid component of the molecule. A probe made from this DNA region hybridized with DNA fragments of other phytopathogenic pseudomonads to varying degrees.
authors.affiliation: Atlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada, Kentville, NS. braung@em.agr.ca
authors.forename: P G
authors.initials: PG
authors.lastname: Braun
authors.forename: P D
authors.initials: PD
authors.lastname: Hildebrand
authors.forename: T C
authors.initials: TC
authors.lastname: Ells
authors.forename: D Y
authors.initials: DY
authors.lastname: Kobayashi
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis; D001937:Brassica / Q000382:microbiology; D003360:Cosmids / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D015723:Gene Library; D005816:Genetic Complementation Test; D008040:Genetic Linkage; D008025:Ligases / Q000378:metabolism; D005810:Multigene Family; D016296:Mutagenesis; D009693:Nucleic Acid Hybridization; D010456:Peptides, Cyclic / Q000096:biosynthesis*; D011551:Pseudomonas fluorescens / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D015183:Restriction Mapping; D013501:Surface-Active Agents / Q000378:metabolism*; D014161:Transduction, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D010456:Peptides, Cyclic; D013501:Surface-Active Agents; D008025:Ligases