Identification of Traits Implicated in the Rhizosphere Competence of Fluorescent Pseudomonads: Description of a Strategy Based on Population and Model Strain Studies

Abstract

The lack of consistency of the beneficial effects of inoculated fluorescent pseudomonads has often been related to their bad survival in the rhizosphere. In this review, we describe the strategy followed over the last decade to study traits involved in the rhizosphere competence of these bacteria. The diversity of indigenous populations associated with plant roots was first compared to that of populations associated with uncultivated soils in order to identify traits that discriminate these populations. The involvement of these bacterial traits in the rhizosphere competence was then assessed by comparing the competitiveness of a wild-type strain to that of mutants affected in the corresponding phenotypes. Finally, traits shared by populations adapted to the rhizosphere were identified by comparing both the competitiveness in the rhizosphere and the metabolism of a collection of bacterial strains. The data yielded indicated that rhizosphere-competent pseudomonads show a specific metabolism especially characterized by the efficiency of the pyoverdine-mediated iron uptake and by the ability to reduce nitrogen oxides. population / diversity / model strain / mutant / metabolism Résumé-Identification de caractères impliqués dans la compétence rhizosphérique des Pseudomonas spp. fluorescents : description d'une stratégie basée sur des études de populations et de souche modèle. Le manque de fiabilité des effets bénéfiques déterminés par les Pseudomonas spp. fluorescents inoculés a souvent été attribué à leur mauvaise survie dans la rhizosphère. Au cours de cette synthèse, nous décrivons la stratégie suivie lors des dix dernières années pour étudier les caractères impliqués dans la compétence rhizosphérique de ces bactéries. La diversité des populations indigènes associées aux racines a d'abord été comparée à celle des populations associées à des sols nus. L'implication de ces caractères bactériens dans la compétence rhizosphérique a ensuite été évaluée en comparant la compétitivité d'une souche modèle à celle de mutants affectés dans les phénotypes correspondants. Finalement, des caractères partagés par les populations adaptées à la rhizosphère ont été identifiés en comparant la compétitivité rhizosphérique et le métabolisme d'une collection de souches. Les données recueillies indiquent que les Pseudomonas spp. fluorescents adaptés à la rhizosphère présentent un métabolisme spécifique caractérisé, en particulier, par l'efficacité de leur système d'acquisition du fer basé sur les pyoverdines et par leur aptitude à réduire les oxydes d'azote. population / diversité / souche modèle / mutant / métabolisme

Screening for fluorescent pseudomonades, isolated from the rhizosphere of tomato, for antagonistic activity toward Clavibacter michiganensis subsp. michiganensis

“…This hypothesis must be analysed by further studies including the three factors: biocontrol agent, pathogen and the host (tomato plant) in a simple and adapted models. In this optic Latour et al (2003), indicated that rhizospherecompetent pseudomonads had a specific metabolism characterized by the efficiency of the pyoverdine mediated iron uptake and by the ability to reduce nitrogen oxides.…”

Evaluation of antibacterial activity of Stenotrophomonas maltophilia against Ralstonia solanacearum under different application conditions

“…Observed lack of consistency of the biological control methods under field conditions may relate to abiotic factors or to soil microbial biodiversity which affects the establishment and colonization of the crops' rhizosphere by the biocontrol agents. Sufficient colonized biocontrol agents along with sustainable activity leads to successful plant protection (Latour et al 2009). Potato is considered an excellent model in developing modern biological control strategies.…”

Influence of Biological Treatment and Ultraviolet Disinfection System on Pseudomonas spp. Diversity in Wastewater as Assessed by Denaturing Gradient Gel Electrophoresis

“…existing in soil or polluted water [6][7][8]. This prominent property makes these microorganisms attractive candidates for use in bioremediation and biocontrol activities [6,9].…”