title: Rhizosphere selection of Pseudomonas putida KT2440 variants with increased fitness associated to changes in gene expression.
abstract: As the interface between plant roots and soil, the rhizosphere is a complex environment where nutrients released by the plant promote microbial growth. Increasing evidences indicate that the plant also exerts a selective pressure on microbial populations in the rhizosphere, favouring colonization by certain groups. In this work, we have designed an experimental setup to begin analysing the evolution of a specific bacterial population in the rhizosphere, using Pseudomonas putida KT2440 as model organism. After several rounds of selection without passage through laboratory growth conditions, derivatives of this strain with increased fitness in the rhizosphere were isolated. Detailed analysis of one of these clones indicated that this effect is specific for rhizosphere conditions and derives from changes in its transcriptional profile in this environment, with 43 genes being differentially expressed with respect to the parental strain. Several of these genes belong to functional categories which could affect stress adaptation and availability of particular nutrients. By inactivating two genes identified as upregulated in the selected clone (coding for a stress-response protein and a rRNA modifying protein), these functions were shown to contribute to rhizosphere fitness. Our data also suggest the existence of different evolutionary pathways leading to increased rhizosphere fitness.
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Quesada
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: Matilde
authors.initials: M
authors.lastname: Fernández
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Soriano
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Barrientos-Moreno
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Llamas
authors.affiliation: Departamento de Protección Ambiental, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, Granada, E-18008, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Espinosa-Urgel