Phenazines in the Environment: Microbes, Habitats, and Ecological Relevance

Abstract

Phenazines, the pigmented, redox-active metabolites produced by certain fluorescent pseudomonads, streptomycetes, and members of a few other bacterial genera, have long been recognized for their broad-spectrum antibiotic activity. Much has been learned in recent years about the synthesis of these compounds and the diverse roles they play in the physiology of the microorganisms that produce them, but surprisingly little is known about their presence and turnover in natural ecosystems or their significance in microbial habitats. Phenazine producers are found throughout nature in association with plant and animal hosts and in terrestrial, freshwater, and marine habitats, and may reach sufficient numbers that the phenazines they produce can be extracted directly from environmental samples. This chapter focuses on recent reports that highlight the diversity of habitats from which phenazine producers have been recovered and the significance of the phenazines they produce in the ecosystems in which they reside.

Characterization of the multiple molecular mechanisms underlying RsaL control of phenazine‐1‐carboxylic acid biosynthesis in the rhizosphere bacterium Pseudomonas aeruginosa PA1201

“…Phenazines are nitrogen-containing aromatic secondary metabolites which are produced and secreted by many different bacterial species. Primarily as a consequence of their redox activity, these compounds affect a broad spectrum of organisms including bacteria, fungi, plants, nematodes, parasites, and humans (Pierson and Pierson, 2006;De Vleesschauwer et al, 2008;Thomashow, 2013;Jayaseelan et al, 2014;Xu et al, 2015). In the opportunistic human pathogen Pseudomonas aeruginosa, the phenazine pyocyanin (PYO) has long been recognized as an important virulence factor, which is important for the establishment of cystic fibrosis lung infections (Lau et al, 2004;Rada and Leto, 2013).…”

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

“…An important diversity of plant-beneficial phenazineproducing Pseudomonas spp. strains has been isolated throughout the world from the rhizosphere of a wide diversity of host plants (Thomashow, 2013). Numerous strains have been isolated as part of screening programs for rhizobacteria able to suppress the growth of plant pathogens (Weller and Cook, 1983;Chin-A-Woeng et al, 1998;Perneel et al, 2007;Kamou et al, 2015).…”

Using non-enzymatic chemistry to influence microbial metabolism

“…Secreted, reduced phenazines support respiration under anaerobic conditions by transferring electrons to nearby extracellular oxidants (frequently Fe 2+/3+ ). This generates ATP through the Entner-Doudoroff pathway, which involves the non-enzymatic regeneration of NAD + from accumulating NADH (Figure 2A) [26]. Phenazines and Fe 2+ have been detected in the sputum of cystic fibrosis patients at levels consistent with this process supporting the anaerobic survival of P. aeruginosa in this environment and contributing to chronic infection [27,28].…”