Phenazine
Streptomyces (terrestrial), Pseudomonas (ubiquitous),Actinomycetes (terrestrial and aquatic), Pelagibacter(aquatic) and Vibrio (aquatic) produce phenazines under the
control of a quorum sensing mechanism. Phenazines are redox-active,
small nitrogen-containing aromatic compounds that are used in a variety
of applications (Velmurugan et al., 2020). The colour intensity ranges
from blue to green to purple to yellow to red to brown. More than 50
nitrogen-containing heterocyclic pigments of bacterial origin are found
in naturally occurring phenazines. Their hues are determined by their
absorption spectra, which contain two peaks in the UV range and at least
one peak in the visible range. Due to their capacity to undergo cellular
redox cycling in the presence of oxygen and reduce NADH and NADPH to
induce the formation of harmful superoxide and hydrogen peroxide, almost
all phenazines are generally detrimental to the growth of bacteria and
fungi. Pantoea agglomerans produces phenazines on apple blooms
that help to control the phytopathogenic Erwinia amylovora , which
causes fire blight (Mavrodi et al., 2010).
Phenazine physiological action is linked to redox homeostasis, which
increases ATP synthesis and membrane potential maintenance (Glasser,
2017). From a biotechnological standpoint, phenazines’ physicochemical
features, such as their oxidation–reduction (redox) properties, vivid
pigmentation, and ability to alter colour with pH and redox state, are
driving their continued study. Phenazines are still employed for a
variety of purposes, including as electron acceptors and donors, fuel
cell components, environmental sensors and biosensors, and as core
components of anticancer drugs (Pierson & Pierson, 2010).