Phenazine-mediated community morphogenesis in the model biocontrol strain Pseudomonas fluorescens 2-79
D. MAVRODI (1), O. Mavrodi (1), L. Elbourne (2), J. Rawalt (1), I. Paulsen (2), D. Weller (3), L. Thomashow (3) (1) The University of Southern Mississippi, U.S.A.; (2) Macquarie University, Australia; (3) USDA-ARS Wheat Health, Genetics and Quality Research Unit, U.S.A.

Winter wheat grown over a million hectares of the Inland Pacific Northwest, USA, supports large populations of phenazine-producing (Phz+) Pseudomonas bacteria. These bacteria produce nanomolar quantities of phenazine-1-carboxylic acid (PCA) in the wheat rhizosphere and provide natural protection against soilborne pathogens. Phz+ pseudomonads thrive in arid areas (<165 mm annual precipitation) that are characterized by cool and moist winters and warm, dry summers. We use Pseudomonas synxantha 2-79 as a model to study the physiological and molecular events involved in the adaptation of Phz+ rhizobacteria to these low water-content habitats. We have produced a high-quality genome assembly of 2-79 and identified candidate pathways involved in the synthesis and uptake of compatible solutes. Our studies also revealed that alterations of genes that regulate the production of PCA strongly affect morphology of colony biofilms under conditions of low oxygen tension. This observation is consistent with the ability of phenazines to facilitate extracellular electron transfer and promote redox balancing. Our findings suggest that phenazines may play an important role in the ability of Phz+ Pseudomonas spp. to sustain active growth and suppress plant pathogens in dry soils that are intermittently rewetted.

Abstract Number: C4-1
Session Type: Concurrent