The RpoS Sigma Factor Negatively Regulates Production of IAA and Siderophore in a Biocontrol Rhizobacterium, Pseudomonas chlororaphis O6

Abstract

The stationary-phase sigma factor, RpoS, influences the expression of factors important in survival of Pseudomonas chlororaphis O6 in the rhizosphere. A partial proteomic profile of a rpoS mutant in P. chlororaphis O6 was conducted to identify proteins under RpoS regulation. Five of 14 differentially regulated proteins had unknown roles. Changes in levels of proteins in P. chlororaphis O6 rpoS mutant were associated with iron metabolism, and protection against oxidative stress. The P. chlororaphis O6 rpoS mutant showed increased production of a pyoverdine-like siderophore, indole acetic acid, and altered isozyme patterns for peroxidase, catalase and superoxide dismutase. Consequently, sensitivity to hydrogen peroxide exposure increased in the P. chlororaphis O6 rpoS mutant, compared with the wild type. Taken together, RpoS exerted regulatory control over factors important for the habitat of P. chlororaphis O6 in soil and on root surfaces. The properties of several of the proteins in the RpoS regulon are currently unknown.

Production of the antifungal compounds phenazine and pyrrolnitrin from Pseudomonas chlororaphis O6 is differentially regulated by glucose

“…Mutants of gacS, rpoS and the first gene in the biosynthetic operon for phenazines, phzA , were generated by gene disruptions and complemented with broad‐host‐range vectors harbouring the wild‐type genes within the mutant strains (Kang et al. 2004, 2007; Oh et al. 2011).…”

The Gac/Rsm Signaling Pathway of a Biocontrol Bacterium, Pseudomonas chlororaphis O6

“…2). The cell envelope changes in the PcO6 rpoS mutant include reduced levels of the outer membrane secretory pore TolC and the inner membrane polyamine translocator PotA (Oh et al, 2013b). Of additional interest is that the rpoS mutant overexpresses two proteins, heme oxidase and the outer membrane heme receptor CirA (Oh et al, 2013b).…”

vfr, A Global Regulatory Gene, is Required for Pyrrolnitrin but not for Phenazine-1-carboxylic Acid Biosynthesis in Pseudomonas chlororaphis G05

“…In P. fluorescens FD6, RetS and Vfr were reported to regulate pyrrolnitrin biosynthesis ( Zhang et al, 2015 , 2016 ). In P. chlororaphis O6, RpoS and GacS deficiency could change the production of pyrrolnitrin ( Oh et al, 2013 ; Park et al, 2018 ). Although pyrrolnitrin can be biosynthesized in many different genera of bacteria and some regulators that mediate its biosynthesis have been identified, its regulatory pathway in detail is not fully made clear.…”