Regulation of the Escherichia coli csgD promoter: interplay between five transcription factors

Abstract

Under stressful conditions in nature, Escherichia coli forms biofilms for long-term survival. Curli fimbriae are an essential architecture for cell-cell contacts within biofilms. Structural components and assembly factors of curli are encoded by two operons, csgBA and csgDEFG. The csgD gene product controls transcription of both operons. Reflecting the response of csgD expression to external stresses, a number of transcription factors participate in the regulation of the csgD promoter. Analysis of the csgD mRNA obtained from E. coli mutants in different transcription factors indicated that CpxR and H-NS act as repressors while OmpR, RstA and IHF act as activators. An acid-stress response regulator, RstA, activates csgD only under acidic conditions. These five factors bind within a narrow region of about 200 bp upstream of the csgD promoter. After pair-wise promoter-binding assays, the increase in csgD transcription in the stationary phase was suggested to be due, at least in part, to the increase in IHF level cancelling the silencing effect of H-NS. In addition, we propose a novel regulation model of this complex csgD promoter through cooperation between the two positive factors (OmpR-IHF and RstA-IHF) and also between the two negative factors (CpxR-H-NS). INTRODUCTIONBacteria can switch from a single-cell planktonic growth mode to a multicellular community (biofilm) mode. During such a growth transition state, cell morphology, physiology and metabolism are markedly altered (PrigentCombaret et al., 2001;Schembri et al., 2003;Beloin et al., 2004;Ren et al., 2004). In single-cell growth mode, cell motility using flagella is critical for adaptation to environments. The master regulator FlhCD complex plays a key role in controlling transcription of a set of genes for flagella formation (Claret & Huges, 2000). When Escherichia coli cells switch their life mode from single planktonic cell growth to multicellular community (biofilm) mode, the genetic system for flagella formation is turned off and the genes involved in cell-cell adhesion are activated. The biofilm matrix is a complex architecture of cell aggregates that are attached on the surface of inorganic solid materials in nature or on eukaryotic tissues in host animals. After a comprehensive analysis of a set of E. coli mutants, each lacking one of 3985 non-essential genes, a total of 110 genes were indicated to be involved in biofilm formation (Niba et al., 2007).During biofilm development, curli fimbriae, the major biofilm component, play a key role in both initial adhesion to solid surfaces and subsequent cell-cell interactions (Vidal et al., 1998;Chapman et al., 2002;Prigent-Combaret et al., 2000). Curli fimbriae also mediate bacterial adhesion to host cells and invasion, and activation of both the proinflammatory response and the immune system (Bian et al., 2000;Zogaj et al., 2001). Accordingly, curli participate in virulence phenotypes (Hammar et al., 1995; Vidal et al., 1998;Bian et al., 2000; Gophna et al., 2001;Cookson et al., 2002). A set of polysacch...

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

“…It has also been shown that IHF activates Pe transcription indirectly via the alleviation of H-NS-mediated repression (van Ulsen et al, 1996). Recent reports further reinforce the role of IHF in alleviating H-NS silencing in Vibrio cholerae (Stonehouse et al, 2008) and in the csgD operon of E. coli (Ogasawara et al, 2010).…”

Novel regulation targets of the metal-response BasS–BasR two-component system of Escherichia coli

“…Also noteworthy is that the anti-silencer LeuO (also a global regulator of membrane function) (Shimada et al, 2011a) and CsgD (the master regulator of biofilm formation) (Ogasawara et al, 2010a(Ogasawara et al, , b, 2011 were regulated by BasR.…”

“…The BasR-binding site on the csgD promoter was determined by DNase I footprinting assay (see Fig. 4), and is mapped on the csgD promoter, on which more than 10 transcription factors associate at various positions, as determined by Ogasawara et al (2010aOgasawara et al ( , b, 2011.…”

Phage insertion in mlrA and variations in rpoS limit curli expression and biofilm formation in Escherichia coli serotype O157 : H7

“…Integration host factor and H-NS, two DNAbending nucleoid proteins, with opposing effects on CsgD expression, contribute to csgD regulation by architectural changes and competition for overlapping binding sites in the intergenic promoter region. Integration host factor is a positive regulator of transcription that binds in two hot spots in the csgD promoter along with other transcription factors Ogasawara et al, 2010b). Although the effects of H-NS have not been fully defined, it has been shown that csgD is suppressed when H-NS is bound to a large region of the csgD promoter that contains both transcription factor-binding hot spots described by Osagawara (Olsén et al, 1993;Ogasawara et al, 2010b).…”