title: New linear lipopeptides produced by Pseudomonas cichorii SF1-54 are involved in virulence, swarming motility, and biofilm formation.
abstract: Pseudomonas cichorii is the causal agent of lettuce midrib rot, characterized by a dark-brown to green-black discoloration of the midrib. Formation of necrotic lesions by several plant-pathogenic pseudomonads is associated with production of phytotoxic lipopeptides, which contribute to virulence. Therefore, the ability of P. cichorii SF1-54 to produce lipopeptides was investigated. A cell-free culture filtrate of SF1-54 showed surfactant, antimicrobial, and phytotoxic activities which are typical for lipopeptides. High-performance liquid chromatography analysis of P. cichorii SF1-54 culture filtrate revealed the presence of seven compounds with lipopeptide characteristics. Two related lipopeptides, named cichofactin A and B, were studied in more detail: they are linear lipopeptides with a decanoic and dodecanoic lipid chain, respectively, connected to the N-terminus of an eight-amino-acid peptide moiety. Both cichofactins are new members of the syringafactin lipopeptide family. Furthermore, two nonribosomal peptide synthethase-encoding genes, cifA and cifB, were identified as responsible for cichofactin biosynthesis. A cifAB deletion mutant no longer produced cichofactins and was impaired in swarming motility but showed enhanced biofilm formation. Upon spray inoculation on lettuce, the cichofactin-deficient mutant caused significantly less rotten midribs than the wild type, indicating that cichofactins are involved in pathogenicity of P. cichorii SF1-54. Further analysis revealed that P. cichorii isolates vary greatly in swarming motility and cichofactin production.
authors: Department of Crop Protection, Ghent University, Ghent, Belgium.
authors: Ellen
authors: E
authors: Pauwelyn
authors: Chien-Jui
authors: CJ
authors: Huang
authors: Marc
authors: M
authors: Ongena
authors: Valérie
authors: V
authors: Leclère
authors: Philippe
authors: P
authors: Jacques
authors: Peter
authors: P
authors: Bleyaert
authors: Herbert
authors: H
authors: Budzikiewicz
authors: Mathias
authors: M
authors: Schäfer
authors: Monica
authors: M
authors: Höfte
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002851:Chromatography, High Pressure Liquid; D055666:Lipopeptides / Q000235:genetics / Q000378:metabolism*; D011549:Pseudomonas / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity* / Q000502:physiology; D014774:Virulence
chemical_list: D055666:Lipopeptides