title: Pseudomonas fluorescensF113 Can Produce a Second Flagellar Apparatus, Which Is Important for Plant Root Colonization.
abstract: The genomic sequence ofPseudomonas fluorescensF113 has shown the presence of a 41 kb cluster of genes that encode the production of a second flagellar apparatus. Among 2,535 pseudomonads strains with sequenced genomes, these genes are only present in the genomes of F113 and other six strains, all but one belonging to theP. fluorescenscluster of species, in the form of a genetic island. The genes are homologous to the flagellar genes of the soil bacteriumAzotobacter vinelandii. Regulation of these genes is mediated by theflhDCmaster operon, instead of the typical regulation in pseudomonads, which is throughfleQ. Under laboratory conditions, F113 does not produce this flagellum and theflhDCoperon is not expressed. However, ectopic expression of theflhDCoperon is enough for its production, resulting in a hypermotile strain. This flagellum is also produced under laboratory conditions by thekinBandalgUmutants. Genetic analysis has shown thatkinBstrongly represses the expression of theflhDCoperon. This operon is activated by the Vfr protein probably in a c-AMP dependent way. The strains producing this second flagellum are all hypermotile and present a tuft of polar flagella instead of the single polar flagellum produced by the wild-type strain. Phenotypic variants isolated from the rhizosphere produce this flagellum and mutation of the genes encoding it, results in a defect in competitive colonization, showing its importance for root colonization.
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Emma
authors.initials: E
authors.lastname: Barahona
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Navazo
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Garrido-Sanz
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Candela
authors.initials: C
authors.lastname: Muriel
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Martínez-Granero
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Redondo-Nieto
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Martín
authors.affiliation: Departamento de Biología, Universidad Autónoma de Madrid Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Rivilla
keywords: FlhDC; genetic island; motility; pseudomonads; rhizosphere