Gre Factors Are Required for Biofilm Formation in Salmonella enterica Serovar Typhimurium by Targeting Transcription of the csgD Gene

Abstract

Rdar biofilm formation of Salmonella typhimurium and Escherichia coli is a common ancient multicellular behavior relevant in cell–cell and inter-organism interactions equally, as in interaction with biotic and abiotic surfaces. With the expression of the characteristic extracellular matrix components amyloid curli fimbriae and the exopolysaccharide cellulose, the central hub for the delicate regulation of rdar morphotype expression is the orphan transcriptional regulator CsgD. Gre factors are ubiquitously interacting with RNA polymerase to selectively overcome transcriptional pausing. In this work, we found that GreA/GreB are required for expression of the csgD operon and consequently the rdar morphotype. The ability of the Gre factors to suppress transcriptional pausing and the 147 bp 5′-UTR of csgD are required for the stimulatory effect of the Gre factors on csgD expression. These novel mechanism(s) of regulation for the csgD operon might be relevant under specific stress conditions.

Pathogenic bacteria experience pervasive RNA polymerase backtracking during infection

“…Consistent with our findings, in S. Typhimurium, Gre factors have been associated with promoting intracellular fitness during oxidative stress by facilitating transcriptional fidelity and elongation of central metabolic genes 46 . They have also been demonstrated to prevent backtracking within one gene, hilD, which encodes a master regulator of SPI genes to promote pathogenesis 47 , and to facilitate biofilm formation through mediating transcription elongation at key effector genes 48 . Similar impact of Gre factors on virulence phenotypes have also been shown in other, highly divergent bacterial species which highlights the conservation of this phenomenon [49][50][51] .…”