Diversity and Evolution of the Phenazine Biosynthesis Pathway

Abstract

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 having various geographic, environmental, and clinical origins to study the distribution and evolution of phenazine genes in members of the genera Pseudomonas, Burkholderia, Pectobacterium, Brevibacterium, and Streptomyces. 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 (rrs, recA, rpoB, atpD, and gyrB) genes revealed that the evolution and dispersal of phenazine genes are 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 the presence of a diverse population of phenazine producers in commercial farm fields located in central Washington state, which provided the first evidence of United States soils enriched in indigenous phenazine-producing bacteria.The naturally occurring phenazines include more than 50 nitrogen-containing heterocyclic pigments of bacterial origin (36). They have characteristic absorption spectra with two peaks in the UV range and at least one peak in the visible range that determines their colors (42). Almost all phenazines are broadly inhibitory to the growth of bacteria and fungi due to their ability to undergo cellular redox cycling in the presence of oxygen and reducing agents (including NADH and NADPH) and cause the accumulation of toxic superoxide and hydrogen peroxide (42). Phenazine-1-carboxylic acid (PCA), 2-hydroxyphenazine-1-carboxylic acid, and phenazine-1-carboxamide (PCN) produced in the rhizosphere by Pseudomonas fluorescens and Pseudomonas chlororaphis inhibit soilborne phytopathogenic fungi (13, 62) and contribute to the natural suppression of Fusarium wilt disease in certain soils in France (45). Phenazines produced by Pantoea agglomerans on apple flowers contribute to suppression of phytopathogenic Erwinia amylovora, which causes fire blight disease (22). Production of pyocyanin (PYO) by Pseudomonas aeruginosa is required for generation of disease symptoms in plants and killing of the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster (40, 54), and it is also critical for lung infection by P. aeruginosa in mice (35). In contrast, some phenazines produced by Streptomyces spp. are not cytotoxic in eukaryotes and have promise as anticancer or anti-infective drugs (36).In addition to the effects of phenazines on other organisms, recent studies have indicated that these compounds directly activate certain transcription factors and act as intercellular signals in P. aeru...

Bacterial Community Morphogenesis Is Intimately Linked to the Intracellular Redox State

“…Similar results have been obtained for flow cell biofilms (8). The phenazines produced by P. aeruginosa vary in structure and chemical properties (9,10), but their redox potentials are such that they all can be reduced by the bacterial cell and react extracellularly with higher-potential oxidants, such as ferric iron and oxygen, acting as electron shuttles between the bacterium and an external substrate (11).…”

Iron induces bimodal population development by Escherichia coli

“…Pseudomonas aeruginosa, along with a variety of other bacteria, produce redox-cycling antibiotics called phenazines (29,41). In susceptible bacteria such as E. coli, phenazines enter the cell and produce superoxide by oxidizing cytoplasmic targets and reducing molecular oxygen (42).…”

Endophytic Nocardiopsis sp. from Zingiber officinale with both antiphytopathogenic mechanisms and antibiofilm activity against clinical isolates

“…The amplification of phz E and phz F genes from ZoA1 was carried out using primers phz Ef (5 0 -GAAGGCGCCA ACTTCGTYATCAA-3 0 )/phz Er (5 0 -GCCYTCGATGA AGTACTCGGTGTG-3 0 ) and Ps_up1 (5 0 -ATCTTCACC CCGGTCAACG-3 0 ) and Ps_low (5 0 -CCRTAGGCCGGTG AGAAC-3 0 ) (Mavrodi et al 2010;Schneemann et al 2011), respectively. PCR parameters for the gene phz E were initial denaturation at 94°C for 2 min, followed by 35 cycles of primer annealing at 54.7°C for 60 s, primer extension at 72°C for 120 s and denaturation at 94°C for 60 s. A final extension was done at 72°C for 7 min.…”