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Phenazines, a nitrogen containing heterocyclic antibiotic biosynthesized by a diverse range of bacteria. Owing its enormous importance as (1) electron shuttles to alternate terminal acceptors in bacteria, (2) modify cellular redox states to modify host response, (3) contributing to biofilm formation and cell signaling, as well as (4) biotechnological applications such as environmental sensor, microbial fuel cell, antitumor, and biocontrol activity attracted attention of scientific community to target phenazine as lead molecule. Similarly, emerging application of phenazines insisted high productivity fermentative process. Current chapter focuses on sources of natural phenazines and impact of nutritional as well as environmental dynamics on fermentative production of phenazine in different bacteria.

Biocontrol ability of Pseudomonas aeruginosa ID 4365, a biocontrol agent of groundnut phytopathogens from marine origin, was previously attributed to the production of pyoverdin type of siderophores. However, pyoverdin-rich supernatants of this organism showed better antifungal activity compared to equivalent amount of purified pyoverdin indicating presence of undetected metabolite(s) in pyoverdin rich supernatants. On the basis of observation that antagonistic activity was iron-dependent and iron-independent, an attempt was made to detect the presence of additional metabolites. In addition to pyoverdin, strain produced additional siderophores, viz. pyochelin and salicylic acid. Two broad spectrum antifungal compounds, viz. pyocyanin and phenazine-1-carboxylic acid, were detected, characterized, and activity against phytopathogens was demonstrated. Iron- and phosphate-dependent co-production of siderophores and phenazines was confirmed. Strain showed additional features like production of hydrogen cyanide, indol-3-acetic acid, and phosphate solubilization.

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