The Yin and Yang of Phenazine Physiology

Abstract

Microorganisms are seldom solitary. They are surrounded by both clonal cells and other members of the local microbial community, and they often exist in, on, or in close proximity to multi-cellular host organisms like plants and humans. Whether in vivo during infection or in situ in the nutrient rich rhizosphere, microorganisms affect each other and the host. Phenazines, a class of secondary metabolites secreted by diverse bacteria, are best known for their antibiotic properties and have been shown to affect a broad spectrum of organisms ranging from bacteria over fungi, plants, nematodes, parasites, and humans. However, phenazines are also involved in numerous aspects of bacterial physiology like survival, iron acquisition, signaling, and biofilm formation in ways that have the potential to increase the fitness of both the phenazine-producing strain and non-producers alike. The overarching theme of this chapter is that phenazines can be beneficial or detrimental to organisms, depending on the milieu and one's perspective. In this chapter, we will highlight specific examples to discuss the yin and yang of phenazine physiology.

The Colorful World of Extracellular Electron Shuttles

“…Flipping through Bergey’s Manual of Systematic Bacteriology (42), one can find numerous examples of organisms that have been named after the colors they produce, for example, Pseudomonas aeruginosa (“rusted copper”; i.e., greenish-blue) (129), Pseudoalteromonas luteoviolacea (“yellow-violet”) (43), and Streptomyces coelicolor (“heavenly color”; Figure 2 b ) (19); yet the biological functions of these defining pigments are seldom discussed. Both old (39) and emerging (48, 55, 93) evidence, however, suggests that literal colorfulness may underpin figurative colorfulness, particularly when the pigment in question has the property of changing color.…”

Transient Proteotoxicity of Bacterial Virulence Factor Pyocyanin in Renal Tubular Epithelial Cells Induces ER-Related Vacuolation and Can Be Efficiently Modulated by Iron Chelators

“…Pyocyanin is believed to play many roles in establishment of P. aeruginosa colonies, including assisting with P. aeruginosa respiration, nutrition, and suppression of competitor bacteria (Grahl et al , 2013). Pyocyanin is a phenazine derivative and can readily act as a potent non-enzymatic redox catalyst and accelerate autoxidation of many substrates essential for cellular redox homeostasis, such as NAD(P)H (Schwarzer et al , 2008) and thiols (O’Malley et al , 2004).…”

Need for Laboratory Ecosystems To Unravel the Structures and Functions of Soil Microbial Communities Mediated by Chemistry

“…Yet we still have much to learn about the biological functions of known metabolites in situ . For example, even relatively simple metabolites such as phenazines, representatives of an extensive class of redox-active metabolites, can play very different roles depending on the microenvironment, from serving as antibiotics, to acting as signaling molecules, to facilitating energy generation, and mediating iron acquisition ( 18 , 19 ). Whether an organism would be expected to resist, be harmed, or even benefit from phenazines depends not only on the state of the environment it inhabits (e.g., oxic or anoxic) but also on its metabolic state and biochemical ecology, i.e., whether it expresses specific phenazine-responsive genes that predict a particular fitness outcome and/or its proximity to other organisms that may degrade or chemically modify phenazines ( 20 ).…”