ARS | Publication request: Evolution of the phenazine biosynthesis pathway and diversity of phenazine-producing Pseudomonas spp. in dryland wheat-producing areas of Washington state

Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: February 16, 2009
Publication Date: N/A

Technical Abstract: Phenazines are versatile secondary metabolites of bacterial origin that function as signaling compounds and contribute to the ecological fitness and pathogenicity of the producing strains. A 2007-2008 survey of commercial dryland fields in central Washington State (annual precipitation <15 in) revealed unexpectedly high populations of phenazine-producing Pseudomonas strains on non-irrigated cereals grown within an area of about three million acres that is roughly bounded by 46.8º and 47.9º N and 117.5º to 119º W. The presence of phenazine-producing Pseudomonas spp. correlated with high levels of the antibiotic phenazine-1-carboxylic acid that were detected on roots of field-grown wheat and barley. Genotyping using the key phenazine biosynthesis gene phzF as a molecular marker revealed that phenazine-producing strains from Washington State soils may form two new species that belong to the P. fluorescens species complex. The investigation of distribution, diversity and genomic context of phenazine genes was further extended using a collection of 82 strains of Pseudomonas, Pectobacterium, Burkholderia, Brevibacterium, and Streptomyces of diverse geographic, environmental and clinical origins. Contrasting phylogenies inferred from sequences of phzF and housekeeping genes (16S, recA, rpoB, atpD, and gyrB) suggested the involvement of horizontal gene transfer in the evolution of the phz biosynthetic pathway in some lineages of bacteria, but at the same time revealed a high degree of conservation of the core phenazine genes in Pseudomonas spp.