Phenazines in plant‐beneficial Pseudomonas spp.: biosynthesis, regulation, function and genomics

Abstract

Plant-beneficial phenazine-producing Pseudomonas spp. are proficient biocontrol agents of soil-dwelling plant pathogens. Phenazines are redox-active molecules that display broad-spectrum antibiotic activity toward many fungal, bacterial and oomycete plant pathogens. Phenazine compounds also play a role in the persistence and survival of Pseudomonas spp. in the rhizosphere. This mini-review focuses on plant-beneficial phenazine-producing Pseudomonas spp. from the P. fluorescens species complex, which includes numerous well-known phenazine-producing strains of biocontrol interest. In this review the current knowledge on phenazine biosynthesis and regulation, the role played by phenazines in biocontrol and rhizosphere colonization, as well as exciting new advances in the genomics of plant-beneficial phenazine-producing Pseudomonas spp. will be discussed.

Insights into plant-beneficial traits of probiotic Pseudomonas chlororaphis isolates

“…The intensity of colony pigmentation in P. chlororaphis strains, when grown on a rich medium, contributes to their ease of isolation and detection during studies. This pigmentation is due to the production of three-ring nitrogen-containing phenazines, which have antimicrobial properties and affect cell signalling [11]. In a 1962 paper [12], the difficulty of identifying an isolate as P. chlororaphis or P. aeruginosa based solely on pigmentation is discussed, because cells of both these species can produce a green colouration.…”

Root‐associated microbes in sustainable agriculture: models, metabolites and mechanisms

“…Several recent reviews have highlighted the biosynthesis, regulation, function and genomics of PCA and other structurally simple phenazines involved in the biocontrol of soilborne fungal, oomycete and even bacterial plant pathogens. The biological activity of these compounds generally is attributed to their ability to produce reactive oxygen species that interfere with the redox homeostasis of the target pathogen.…”

“…For example, whereas PCA was the most active against G. graminis var . tritici, phenazine‐1‐carboxamide was more effective against tomato root rot than either PCA or its hydroxylated derivatives, and a hydroxylated PCA derivative was the most inhibitory in vitro to Alternaria brassicae . There are few reports of phenazine activity against foliar pathogens, but the commercial fungicide shenqinmycin, with PCA as its main active ingredient, is widely used in southern China to control sheath blight of rice and notably, phenazine‐1‐carboxamide produced by P. piscium on the heads of wheat infected with the head blight pathogen Fusarium graminearum has been shown to interfere with histone acetylation, suppressing fungal growth, virulence, and mycotoxin biosynthesis …”

“…Moreover, the turnover of 15 N-labeled bacterial biomass on nonirrigated roots was slower and in several instances, the 15 N was incorporated into root cell walls, potentially influencing crop nutrition and soil organic matter retention. 10 Several recent reviews [11][12][13] have highlighted the biosynthesis, regulation, function and genomics of PCA and other structurally simple phenazines involved in the biocontrol of soilborne fungal, oomycete and even bacterial plant pathogens. The biological activity of these compounds generally is attributed to their ability to produce reactive oxygen species that interfere with the redox homeostasis of the target pathogen.…”

Global landscape of phenazine biosynthesis and biodegradation reveals species-specific colonization patterns in agricultural soils and crop microbiomes

“…Phenazines are heterotricyclic N-containing metabolites mainly produced by bacteria in soil and plantroot microbiomes (Biessy and Filion, 2018;Mavrodi et al, 2010), though some are also important in chronic human infections (Sismaet et al, 2016;Wilson et al, 1988). Members of this diverse family of redox-active metabolites act as broad-spectrum antibiotics by generating toxic reactive oxygen species (ROS) as well as interfering with cellular respiration chains (Baron et al, 1989;Perry and Newman, 2019).…”