The RpoS Sigma factor relieves H‐NS‐mediated transcriptional repression of <i>csgA</i>, the subunit gene of fibronectin‐binding curli in <i>Escherichia coli</i>

Olsén, Arne; Arnqvist, Anna; Hammar, Mårten; Sukupolvi, Soila; Normark, Staffan

doi:10.1111/j.1365-2958.1993.tb01143.x

Cited by 267 publications

(274 citation statements)

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“…among UTI strains (25 %). Highly regulated rdar morphotype expression seems to be a characteristic of a subset of enterobacterial pathovars (Olsen et al, 1993;Römling et al, 2003;Sjöbring et al, 1994;Zogaj et al, 2003). To summarize, in contrast to Salmonella serovars, variation of expression of curli fimbriae and cellulose was common among commensal E. coli strains, with eight morphotypes discriminated.…”

Section: Discussionmentioning

confidence: 99%

Expression of cellulose and curli fimbriae by Escherichia coli isolated from the gastrointestinal tract

Bokranz

Xiao-da

Tschäpe

et al. 2005

Journal of Medical Microbiology

228

235

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Escherichia coli colonizes the gastrointestinal tract of humans; however, little is known about the features of commensal strains. This study investigated whether expression of the biofilm extracellular matrix components cellulose and curli fimbriae is found among commensal isolates. Fifty-two E. coli strains were isolated from faecal samples and, as a control, 24 strains from urinary tract infections were also used. Faecal isolates were characterized by serotyping and phylogenetically grouped by PCR. The genotype was determined by PFGE and the presence of virulence factors was assessed. Co-expression of cellulose and curli fimbriae at 28 8C and 37 8C was typical for faecal isolates, while urinary tract infection strains typically expressed the extracellular matrix components at 28 8C only. Knockout studies in a representative faecal isolate revealed that the response regulator CsgD regulated cellulose and curli fimbriae, as found previously in Salmonella enterica. In contrast to S. enterica, at 37 8C pellicle formation occurred in the absence of cellulose and curli fimbriae. The gastrointestinal tract represents a source of biofilm-forming bacteria, which can spread to susceptible sites.

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Section: Discussionmentioning

confidence: 99%

Expression of cellulose and curli fimbriae by Escherichia coli isolated from the gastrointestinal tract

Bokranz

Xiao-da

Tschäpe

et al. 2005

Journal of Medical Microbiology

228

235

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“…In E. coli K-12, this complex regulatory network controls initial adhesion and biofilm formation via regulation of the csgD gene (Prigent-Combaret et al, 2001). It involves H-NS (Arnqvist et al, 1992;Olsen et al, 1993), IHF (Gerstel et al, 2003), Crl (Arnqvist et al, 1994;Bougdour et al, 2004;Hammar et al, 1995) and MlrA (Brown et al, 2001). The OmpR/EnvZ (Prigent-Combaret et al, 2001;Romling et al, 1998) and CpxR/A (Dorel et al, 1999;Otto & Silhavy, 2002;Prigent-Combaret et al, 2001) phosphorelays also control curli expression.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2005

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Curli are necessary for the adherence of Escherichia coli to surfaces, and to each other, during biofilm formation, and the csgBA and csgDEFG operons are both required for their synthesis. A recent survey of gene expression in Pseudomonas aeruginosa biofilms has identified tolA as a gene activated in biofilms. The tol genes play a fundamental role in maintaining the outer-membrane integrity of Gram-negative bacteria. RcsC, the sensor of the RcsBCD phosphorelay, is involved, together with RcsA, in colanic acid capsule synthesis, and also modulates the expression of tolQRA and csgDEFG. In addition, the RcsBCD phosphorelay is activated in tol mutants or when Tol proteins are overexpressed. These results led the authors to investigate the role of the tol genes in biofilm formation in laboratory and clinical isolates of E. coli. It was shown that the adherence of cells was lowered in the tol mutants. This could be the result of a drastic decrease in the expression of the csgBA operon, even though the expression of csgDEFG was slightly increased under such conditions. It was also shown that the Rcs system negatively controls the expression of the two csg operons in an RcsA-dependent manner. In the tol mutants, activation of csgDEFG occurred via OmpR and was dominant upon repression by RcsB and RcsA, while these two regulatory proteins repressed csgBA through a dominant effect on the activator protein CsgD, thus affecting curli synthesis. The results demonstrate that the Rcs system, previously known to control the synthesis of the capsule and the flagella, is an additional component involved in the regulation of curli. Furthermore, it is shown that the defect in cell motility observed in the tol mutants depends on RcsB and RcsA. INTRODUCTIONThe ability of bacteria to recognize and adhere to a specific surface is a fundamental aspect of microbial ecology and pathogenesis. Bacterial adhesins and fimbriae confer specific recognition and adhesion to diverse target molecules, such as mammalian host tissue components or inorganic materials. Curli are highly adhesive proteinaceous fibres involved in this process that are produced by Escherichia coli (Vidal et al., 1998) and Salmonella (Collinson et al., 1991). The genes necessary for curli formation are clustered in the csgBA and csgDEFG operons. CsgA encodes the curlin subunit, CsgB is thought to nucleate CsgA curlin fibres (Bian & Normark, 1997), CsgD is a transcriptional activator of the csgBA operon, and CsgE, CsgF and CsgG are three putative curli assembly factors. The lipoprotein CsgG localizes to the inner leaflet of the outer membrane and may serve as a curli assembly platform (Loferer et al., 1997); CsgE and CsgF are thought to be chaperone-like proteins (Chapman et al., 2002). The csg genes appear to be expressed in environmental strains, clinical isolates and some laboratory strains of E. coli.Regulation of curli synthesis is carried out through a complex network of interactions between the transcription factors and the csg regulatory region. Nine regulators have ...

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“…(ii) In at least some cases, deletion of DNA near the promoter relieves the silencing of transcription, increasing expression to that seen in the mutants, suggesting that the promoter itself is capable of high levels of transcription initiation (24). (iii) For several promoters, a positive activator or other DNA-binding protein can overcome the silencing and allow high levels of transcription initiation (8,23).…”

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hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

et al. 1995

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Transcription of the hly operon of transmissible plasmids in Escherichia coli is subject to a tight regulation which also involves various chromosomal genes, such as hha. We have identified a 200-bp region within the hlyC gene, designated hlyM, which modulates hemolysin expression. The deletion of hlyM increased the activity of hly::galK fusion 20-fold. hlyM does not contain any internal promoter, nor is it capable of acting in trans. Our data suggest that the chromosomal Hha protein interacts with hlyM in order to silence the hly promoter. In addition, hlyR, a positive activator of hemolysin expression, seems to suppress the modulatory effect dictated by the Hha protein on the hlyM region.Synthesis and secretion of hemolysin are determined by the hly operon located either on the chromosome or on conjugative plasmids (10). Transcription of the hly operon produces a major 4-kb hlyCA transcript and a minor 8-kb hlyCABD transcript (31). The two transcripts initiate at the same promoter, located upstream of the hlyC gene (12, 31). The minor transcript is thought to be produced by readthrough, or antitermination, at a Rho-independent transcriptional terminator located between hlyA and hlyB (15). Similar patterns of expression have been reported for the leukotoxins of Pasteurella (27) and Actinobacillus (26) species.In the case of the plasmid hly operons, a 600-bp sequence (hlyR) located 1.5 kb upstream of hlyC is known to increase hemolysin expression (29). The primary mechanism by which hlyR exerts its action has been proposed to be antitermination at the hlyA-hlyB transcriptional terminator (15,16).Hemolysin expression is a rather complex process in which chromosomal genes are involved as well. Three of them, tolC (30), hha (9, 21), and more recently sfrB (1), have been identified. The hha gene was identified during analysis of hemolysin expression in cells harboring the hemolytic recombinant plasmid pANN202-312, which contains the cluster hlyCABD from

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The RpoS Sigma factor relieves H‐NS‐mediated transcriptional repression of csgA, the subunit gene of fibronectin‐binding curli in Escherichia coli

Cited by 267 publications

References 50 publications

Expression of cellulose and curli fimbriae by Escherichia coli isolated from the gastrointestinal tract

Expression of cellulose and curli fimbriae by Escherichia coli isolated from the gastrointestinal tract

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

hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

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