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What makes phenazine-producing Pseudomonas spp. good rhizosphere colonizers?

Antoine Zboralski: Université de Moncton

<div>Phenazine-producing <em>Pseudomonas </em>spp. play an active part in the suppressive ability of particular soils against phytopathogenic agents such as <em>Gaeumannomyces graminis</em> var. <em>tritici </em>or <em>Fusarium oxysporum</em>. Their inhibitory efficiency is strongly related to their ability to colonize the soil surrounding plant roots: the rhizosphere. To better characterize the multiple factors involved in rhizosphere colonization, we assembled a collection of 63 worldwide representative phenazine-producing <em>Pseudomonas </em>strains. The different strains were inoculated in the rhizosphere of <em>Arabidopsis thaliana </em>grown in peat-based potting soil. Rhizosphere colonization was then assessed by quantitative PCR using a newly developed TaqMan probe/primer set targeting the phenazine biosynthesis operon. In parallel, we also investigated the metabolic profiles of the 63 strains using the BIOLOG phenotype microarray technology. In total, 270 out of 758 tested substrates were differentially metabolized by the 63 strains. Substrate utilization profiles correlated with previously obtained phylogenomic data. The strains also exhibited differential rhizosphere colonization capabilities on <em>A. thaliana</em>. These results have led to the identification of specific genes potentially involved in rhizosphere colonization abilities. Their implication are presently being assessed through a reverse genetic approach.</div>