Escherichia coli tol and rcs genes participate in the complex network affecting curli synthesis

Vianney, Anne; Jubelin, Grégory; Renault, Sophie; Dorel, Corinne; Lejeune, Philippe; Lazzaroni, Jean-Claude

doi:10.1099/mic.0.27913-0

Cited by 74 publications

(57 citation statements)

References 55 publications

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“…E. coli surface appendages reported to be affected by the Rcs system include flagella, curli, and type 1 fimbriae, which are involved in biofilm formation under different growth conditions (42,48,70). RcsB, together with its cofactor RcsA, represses the activity of the flagellar master operon flhDC (15) and the two csg operons for curli expression (13,69). In contrast, RcsB positively controls the expression of type 1 fimbriae by controlling the transcription of the site-specific recombinase genes fimB and fimE, thereby favoring the "phase-on" orientation of the fimA promoter (62).…”

Section: Resultsmentioning

confidence: 99%

The Response Regulator RcsB Activates Expression of Mat Fimbriae in Meningitic Escherichia coli

et al. 2012

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The common colonization factor of Escherichia coli, the Mat (also termed ECP) fimbria, functions to advance biofilm formation on inert surfaces as well as bacterial adherence to epithelial cells and subsequent colonization. We used global mini-Tn5 transposon mutagenesis to identify novel regulators of biofilm formation by the meningitic E. coli isolate IHE 3034. Of the 4,418 transformants, we found 17 that were impaired in biofilm formation. Most of these mutants were affected in lipopolysaccharide synthesis and were reduced in growth but not in Mat fimbria expression. In contrast, two mutants grew well but did not express Mat fimbria. The insertions in these two mutants were located at different sites of the rcsB gene, which encodes a DNA-binding response regulator of the Rcs response regulon. The mutations abrogated temperature-dependent biofilm formation by IHE 3034, and the phenotype correlated with loss of mat expression. The defect in biofilm formation in the rcsB mutant was reversed upon complementation with rcsB as well as by overexpression of structural mat genes but not by overexpression of the fimbria-specific activator gene matA. Monitoring of the mat operon promoter activity with chromosomal reporter fusions showed that the RcsB protein and an RcsAB box in the mat regulatory region, but not RcsC, RcsD, AckA, and Pta, are essential for initiation of mat transcription. Gel retardation assays showed that RcsB specifically binds to the mat promoter DNA, which enables its function in promoting biofilm formation by E. coli. Bacterial growth in biofilm provides many advantages compared to a planktonic lifestyle. In a biofilm, bacteria gain resistance to antimicrobial agents and defense systems of the host as well as better protection from predation and other environmental assaults, such as hydrodynamic shear forces and desiccation (9,20). This protective effect probably explains why bacterial biofilm growth is common in many environmental, clinical, and industrial settings and why it complicates the elimination of biofilmassociated bacteria. Following initial attachment to a surface, bacterial cells undergo profound physiological and metabolic adjustments along the transition from a single-cell state into a communal lifestyle. This complex process of biofilm development requires integration of a variety of environmental, cell-to-cell, and intracellular signals into an interplay of regulatory networks (25,50).Escherichia coli is a commensal bacterium in the gastrointestinal tract as well as a pathogen of intra-and extraintestinal body sites. E. coli expresses an arsenal of surface appendages that confer tissue-adhesive and biofilm formation capacity upon the bacterium (27, 28). Meningitis-associated and temperature-regulated (Mat) fimbriae (or E. coli common pili [ECP]) promote biofilm growth on inert surfaces (34) and adhesion to human epithelial cell lines in vitro (4,32,53,55). Available data also indicate that the fimbria is expressed in vivo in the human body and in the intestine of infant mouse (32, 5...

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Section: Resultsmentioning

confidence: 99%

The Response Regulator RcsB Activates Expression of Mat Fimbriae in Meningitic Escherichia coli

et al. 2012

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“…Thus, none of the 13 genes preceded by RcsB-RcsB binding sites was required for spheroplast recovery. Of the 5 genes containing RcsA-RcsB binding sites, the RcsARcsB heterodimer negatively regulates csgD and flhD (27,28). Thus, an Rcs-deficient mutant may produce higher levels of CsgD or FlhD than the wild type, which might in turn prevent spheroplast recovery.…”

Section: Fig 1 Organization Of the Periplasm And Peptidoglycan In Recmentioning

confidence: 99%

Colanic Acid Intermediates Prevent De Novo Shape Recovery of Escherichia coli Spheroplasts, Calling into Question Biological Roles Previously Attributed to Colanic Acid

Ranjit

Young

2016

J Bacteriol

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After losing their protective peptidoglycan, bacterial spheroplasts can resynthesize a cell wall to recreate their normal shape. In Escherichia coli, this process requires the Rcs response. In its absence, spheroplasts do not revert to rod shapes but instead form enlarged spheroids and lyse. Here, we investigated the reason for this Rcs requirement. Rcs-deficient spheroids exhibited breaks and bulges in their periplasmic spaces and failed to synthesize a complete peptidoglycan cell wall, indicating that the bacterial envelope was defective. To determine the Rcs-dependent gene(s) required for shape recovery, we tested spheroplasts lacking selected RcsB-regulated genes and found that colanic acid (CA) biosynthesis appeared to be involved. Surprisingly, though, extracellular CA was not required for recovery. Instead, lysis was caused by mutations that interrupted CA biosynthesis downstream of the initial glycosyl transferase, WcaJ. Deleting wcaJ prevented lysis of spheroplasts lacking ensuing steps in the pathway, and providing WcaJ in trans to a mutant lacking the entire CA operon triggered spheroplast enlargement and lysis. Thus, CA is not required for spheroplast recovery. Instead, CA intermediates accumulate as dead-end products which inhibit recovery of wallless cells. The results strongly imply that CA may not be required for the survival E. coli L-forms. More broadly, these findings mandate that previous conclusions about the role of colanic acid in biofilm formation or virulence must be reevaluated. IMPORTANCEWall-less bacteria can resynthesize their walls and recreate a normal shape, which in Escherichia coli requires the Rcs response. While attempting to identify the Rcs-dependent gene required for shape recovery, we found that colanic acid (CA) biosynthesis appeared to be involved. Surprisingly, though, cell death was caused by mutations that interrupted CA biosynthesis downstream of the initial step in the pathway, creating dead-end compounds that inhibited recovery of wall-less cells. When testing for the biological role of CA, most previous experiments used mutants that would accumulate these deadly intermediates, meaning that all prior conclusions must be reexamined to determine if the results were caused by these lethal side effects instead of accurately reflecting the biological purpose of CA itself. Bacterial cell shape is determined by coordinated and dynamic interactions among cytoskeletal elements, peptidoglycan synthesis, and cell division (as reviewed in references 1 and 2), and the wall and some of its morphological characteristics contribute to cell survival in suboptimal or hostile environments (3). For example, the host immune system elaborates several antibacterial factors, including lysozyme, cationic antimicrobial peptides, and protein complexes, which target the cell envelope and trigger bacterial lysis (4-6). In particular, lysozyme removes the peptidoglycan wall and leads to cell rupture. However, such cells may not lyse if they are immersed in an osmotically protective medi...

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“…As the expression of colanic acid is required for the maturation of biofilms formed by E. coli, this suggests a positive role for the Rcs phosphorelay in the regulation of biofilm maturation (Danese et al, 2000b). On the other hand, activation of the Rcs phosphorelay has been shown to repress the expression of genes encoding surface adhesins, such as antigen 43 (Ag43) and curli, and it has been reported that overproduction of RcsB (a situation that mimics the activation of the Rcs phosphorelay) inhibits the expression of the flhDC operon, encoding the master regulators of flagella biosynthesis (Ferrières & Clarke, 2003;Francez-Charlot et al, 2003;Vianney et al, 2005). Therefore, the activation of the Rcs phosphorelay would be expected to have a negative effect on the attachment of cells to a surface.…”

Section: Introductionmentioning

confidence: 99%

Elevated levels of σ S inhibit biofilm formation in Escherichia coli: a role for the Rcs phosphorelay

2009

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The Rcs phosphorelay is composed of RcsC, RcsD and the response regulator RcsB, and this signalling pathway has been implicated in virulence and biofilm formation in many enteric bacteria. It was previously shown that a mutation in rcsC resulted in defective biofilm formation in Escherichia coli [Ferrières, L. & Clarke, D. J. (2003) Mol Microbiol 50, 1665–1682]. To identify the molecular mechanisms underlying the observed biofilm defect we carried out a screen looking for suppressor mutants that restored biofilm formation in the rcsC mutant background. One of the mutants was identified to be in rprA, a gene encoding a small RNA molecule that is involved in the post-transcriptional control of the alternative sigma factor, σ S. The expression of rprA is regulated by the Rcs phosphorelay, and there are elevated σ S levels present in the rcsC mutant due to the overexpression of rprA in this background. Using different approaches, we have established that the increase in σ S levels is responsible for the biofilm defect. Therefore, the Rcs phosphorelay is involved in maintaining appropriate levels of σ S during biofilm formation in E. coli.

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Escherichia coli tol and rcs genes participate in the complex network affecting curli synthesis

Cited by 74 publications

References 55 publications

The Response Regulator RcsB Activates Expression of Mat Fimbriae in Meningitic Escherichia coli

The Response Regulator RcsB Activates Expression of Mat Fimbriae in Meningitic Escherichia coli

Colanic Acid Intermediates Prevent De Novo Shape Recovery of Escherichia coli Spheroplasts, Calling into Question Biological Roles Previously Attributed to Colanic Acid

Elevated levels of σ S inhibit biofilm formation in Escherichia coli: a role for the Rcs phosphorelay

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