Diversity and Evolution of the Phenazine Biosynthesis Pathway

Phenazines are versatile secondary metabolites of bacterial origin that function in biological control of plant pathogens and contribute to the ecological fitness and pathogenicity of the producing strains. In this study, we employed a collection of 94 strains of various geographic, environmental and clinical origins to study the distribution and evolution of phenazine genes in members of Pseudomonas, Burkholderia, Pectobacterium, Brevibacterium and Streptomyces genera. Our results confirmed the diversity of phenazine producers and revealed that most of them appear to be soil-dwelling and/or plant-associated species. Genome analyses and comparisons of phylogenies inferred from sequences of the key phenazine biosynthesis phzF and housekeeping genes (rrs, recA, rpoB, atpD, and gyrB) revealed that the evolution and dispersal of phenazine genes is driven by mechanisms ranging from conservation in Pseudomonas spp. to horizontal gene transfer in Burkholderia spp. and Pectobacterium spp. DNA extracted from cereal crop rhizospheres and screened for the presence of phzF contained sequences consistent with a diverse population of phenazine-producers in commercial farm fields located in central Washington State, thus providing the first evidence of U.S. soils enriched in indigenous phenazine-producing bacteri