Phenazine-producing Pseudomonas spp. in the rhizosphere

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Pseudomonas spp. are aerobic, Gram-negative bacteria ubiquitously found in soils. They are particularly well suited for plant root colonization and many plant-beneficial strains display biocontrol activity against plant pathogens through various mechanisms, including antibiosis. Among the wide array of antibiotics produced by plant-beneficial Pseudomonas spp., phenazines display broad-spectrum antimicrobial activity. Different phenazine derivatives have been shown to play a crucial role in the biocontrol of several pathogens in various plant systems as well as being involved in rhizocompetence (i.e. the capacity to colonize the rhizosphere) and biofilm formation in the rhizosphere. Plant-beneficial Pseudomonas spp. possess a large genome which displays a mosaic structure with genes segregating between the core genome, responsible for essential cellular processes, and the accessory genome, often unique to one or few strains, and responsible for the variability observed among strains. The genomic diversity and plasticity of plant-beneficial Pseudomonas spp. come from their accessory genomes. Recently, our laboratory assembled the largest worldwide collection of plant-beneficial phenazine-producing Pseudomonas spp. A collection of 63 representative organisms isolated from 18 countries were chosen to account for the large diversity of host plants and environments from where they were isolated, their worldwide distribution, their taxonomical diversity, and the array of phenazine derivatives produced. The sequencing and annotation of their genomes has recently been completed by our laboratory. This unique large data set will be used as a starting point for this research project. The primary goal of this research is to better characterize and understand how plant-beneficial phenazine-producing Pseudomonas spp. influence the ecology of the rhizosphere, leading to improved plant health, and protection against various plant diseases. The specific goals are to: 1) Characterize and compare the worldwide diversity of plant-beneficial phenazine-producing Pseudomonas spp. at the genomics and functional levels. 2) Characterize and contrast the mechanisms employed by plant-beneficial phenazine-producing Pseudomonas spp. against bacterial, oomycete and fungal plant pathogens. 3) Identify key genetic determinants in plant-beneficial phenazine-producing Pseudomonas spp. involved in rhizocompetence.A better understanding of the diversity, ecology and genomics of plant-beneficial phenazine-producing Pseudomonas spp., as well as the mechanisms involved in their rhizocompetence and biocontrol of plant pathogens is required to ensure the successful development, formulation and commercialisation of some of these organisms as biopesticides. This research program will address this gap in knowledge.