title: Physiological and transcriptomic characterization of a fliA mutant of Pseudomonas putida KT2440.
abstract: Pseudomonas putida KT2440 encodes 23 alternative sigma factors. The fliA gene, which encodes σ(28) , is in a cluster with other genes involved in flagella biosynthesis and chemotaxis. Reverse transcriptase-PCR revealed that this cluster is comprised of four independent transcriptional units: flhAF, fleNfliA, cheYZA and cheBmotAB. We generated a nonpolar fliA mutant by homologous recombination and tested its motility, adhesion to biotic and abiotic surfaces, and responses to various stress conditions. The mutant strain was nonmotile and exhibited decreased capacity to bind to corn seeds, although its ability to colonize the rhizosphere of plants was unaffected. The mutant was also affected in binding to abiotic surfaces and its ability to form biofilms decreased by almost threefold. In the fliA mutant background expression of 25 genes was affected: two genes were upregulated and 23 genes were downregulated. In addition to a number of motility and chemotaxis genes, the fliA gene product is also necessary for the expression of some genes potentially involved in amino acid utilization or stress responses; however, we were unable to assign specific phenotypes linked to these genes since the fliA mutant used the same range of amino acids as the parental strain, and was as tolerant as the wild type to stress imposed by heat, antibiotics, NaCl, sodium dodecyl sulfate, H2 O2 and benzoate. Based on the sequence alignment of promoters recognized by FliA and genome in silico analysis, we propose that P. putidaσ(28) recognizes a TCAAG-t-N12 -GCCGATA consensus sequence located between -34 and -8 and that this sequence is preferentially associated with an AT-rich upstream region.
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, E-18008 Granada, Spain. Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden. Unidad Asociada de Contaminación Atmosférica, CSIC-Universidad de Huelva, Huelva, Spain.
authors.forename: José Juan
authors.initials: JJ
authors.lastname: Rodríguez-Herva
authors.forename: Estrella
authors.initials: E
authors.lastname: Duque
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Molina-Henares
authors.forename: Gloria
authors.initials: G
authors.lastname: Navarro-Avilés
authors.forename: Pieter
authors.initials: P
authors.lastname: Van Dillewijn
authors.forename: Jesús
authors.initials: J
authors.lastname: De La Torre
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Molina-Henares
authors.forename: Ana Sánchez-de
authors.initials: AS
authors.lastname: La Campa
authors.forename: F Ann
authors.initials: FA
authors.lastname: Ran
authors.forename: Ana
authors.initials: A
authors.lastname: Segura
authors.forename: Victoria
authors.initials: V
authors.lastname: Shingler
authors.forename: Juan-Luis
authors.initials: JL
authors.lastname: Ramos