The leucine-responsive regulatory protein binds to the fim switch to control phase variation of type 1 fimbrial expression in Escherichia coli K-12

Gally, David L.; Rucker, Thomas; Blomfield, Ian C.

doi:10.1128/jb.176.18.5665-5672.1994

Cited by 99 publications

(104 citation statements)

References 23 publications

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“…Likewise, a shift to a lower antibiotic concentration for the ⌬hns and ⌬lrp backgrounds harboring pBAD-tosR-His 6 does not perturb TosR regulation itself; the lower antibiotic concentration did not perturb TosR-mediated regulation in the wild-type E. coli CFT073 background (data not shown). As for H-NS, Lrp is also a global regulator (19,22,(37)(38)(39)(59)(60)(61)(62)(63)(64)(65)(66)(67). Therefore, it remains unclear if additional gene products also supplement Lrp-and TosRmediated positive regulation of the tos operon.…”

Section: Resultsmentioning

confidence: 99%

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Regulation of Expression of Uropathogenic Escherichia coli Nonfimbrial Adhesin TosA by PapB Homolog TosR in Conjunction with H-NS and Lrp

Engstrom

Mobley

2016

Infect Immun

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Urinary tract infections (UTIs) are a major burden to human health. The overwhelming majority of UTIs are caused by uropathogenic Escherichia coli (UPEC) strains. Unlike some pathogens, UPEC strains do not have a fixed core set of virulence and fitness factors but do have a variety of adhesins and regulatory pathways. One such UPEC adhesin is the nonfimbrial adhesin TosA, which mediates adherence to the epithelium of the upper urinary tract. The tos operon is AT rich, resides on pathogenicity island aspV, and is not expressed under laboratory conditions. Because of this, we hypothesized that tosA expression is silenced by H-NS. Lrp, based on its prominent function in the regulation of other adhesins, is also hypothesized to contribute to tos operon regulation. Using a variety of in vitro techniques, we mapped both the tos operon promoter and TosR binding sites. We have now identified TosR as a dual regulator of the tos operon, which could control the tos operon in association with H-NS and Lrp. H-NS is a negative regulator of the tos operon, and Lrp positively regulates the tos operon. Exogenous leucine also inhibits Lrp-mediated tos operon positive regulation. In addition, TosR binds to the pap operon, which encodes another important UPEC adhesin, P fimbria. Induction of TosR synthesis reduces production of P fimbria. These studies advance our knowledge of regulation of adhesin expression associated with uropathogen colonization of a host. U rinary tract infections (UTIs), which are among the most common bacterial infections of humans (1), can occur in otherwise healthy individuals when bacteria colonizing the gastrointestinal tract gain access to the periurethral area. Most individuals with UTIs develop an infection of the bladder, referred to as cystitis (1). However, the infecting bacterium may ascend the ureters to infect the kidneys (pyelonephritis) and, in some cases, enter the bloodstream leading to bacteremia and sometimes fatal urosepsis (1-4).A diverse group of extraintestinal pathogenic Escherichia coli strains, referred to as uropathogenic E. coli (UPEC), cause the overwhelming majority of uncomplicated UTIs (2, 5). While numerous UPEC virulence factors have been identified, including adhesins, motility systems, toxins, and iron acquisition systems, a core set of virulence factors has not been strictly defined (6-8). However, it is critical to understand specific virulence factors and how they are regulated.Previous work identified and characterized the E. coli repeatsin-toxin (RTX) nonfimbrial adhesin TosA (i.e., type one secretion as the predicted secretion mechanism) (7, 9-13). In particular, it was noted that tosA and the other tos operon genes have poor in vitro expression (9-11). TosA, a Ͼ250-kDa surface-exposed protein, mediates UPEC adherence to epithelial cells derived from the upper urinary tract (9). This is in contrast to a number of other RTX proteins, which are fully secreted into the extracellular milieu and act as toxins (14-18). We estimated that ϳ32% of UPEC strains carry genes enc...

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Section: Resultsmentioning

confidence: 99%

“…Some genes regulated by Lrp are positively or negatively regulated by exogenous leucine (63)(64)(65)67). To test whether exogenous leucine positively or negatively regulates the tos operon, we performed our pBAD-lrp overexpression assay in the CFT073 ⌬tosR background in M9 minimal medium with and without exogenous leucine (10 mM).…”

Section: Resultsmentioning

confidence: 99%

Regulation of Expression of Uropathogenic Escherichia coli Nonfimbrial Adhesin TosA by PapB Homolog TosR in Conjunction with H-NS and Lrp

Engstrom

Mobley

2016

Infect Immun

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“…The orientation was confirmed by restriction analysis. The minimal fim switch unit was cloned into pDG19, using primers 135F and 136F, generating pNJH79 for allelic exchange into strain BGEC144, generating strain ZAP973, as described in Gally et al (1994). Insertion was confirmed by specific PCR.…”

Section: Methodsmentioning

confidence: 99%

Demonstration of regulatory cross-talk between P fimbriae and type 1 fimbriae in uropathogenic Escherichia coli

et al. 2006

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The majority of Escherichia coli strains isolated from urinary tract infections have the potential to express multiple fimbriae. Two of the most common fimbrial adhesins are type 1 fimbriae and pyelonephritis-associated pili (Pap). Previous research has shown that induced, plasmid-based expression of a Pap regulator, papB, and its close homologues can prevent inversion of the fim switch controlling the expression of type 1 fimbriae. The aim of the present study was to determine if this cross-regulation occurs when PapB is expressed from its native promoter in the chromosome of E. coli K-12 and clinical isolates. The regulation was examined in three ways: (1) mutated alleles of the pap regulatory region, including papB and papI, that maintain the pap promoter in either the off or the on phase were exchanged into the chromosome of both E. coli K-12 and the clinical isolate E. coli CFT073, and the effect on type 1 fimbrial expression was measured; (2) type 1 fimbrial expression was determined using a novel fimS : : gfp + reporter system in mutants of the clinical isolate E. coli 536 in which combinations of complete fimbrial clusters had been deleted; (3) type 1 fimbrial expression was determined in a range of clinical isolates and compared with both the number of P clusters and their expression. All three approaches demonstrated that P expression represses type 1 fimbrial expression. Using a number of novel genetic approaches, this work extends the initial finding that PapB inhibits FimB recombination to the impact of this regulation in clinical isolates. INTRODUCTIONUrinary tract infections (UTIs) are common, affecting a large proportion of the population. It is estimated that 20 % of women develop a UTI in their lifetime, and antibiotic treatment results in approximately 110 000 prescriptions per million inhabitants per annum in Europe (Naber, 2000). Escherichia coli strains are the predominant cause of uncomplicated UTIs, responsible for between 60 and 80 % of the cases reported in the UK each year (Graham & Galloway, 2001). Many infections are asymptomatic, especially in the elderly (Nicolle, 2001), but others result in cystitis. If the infection ascends to the kidney, then pyelonephritis can occur. Such infections are a significant origin of Gramnegative sepsis.Fimbrial adhesins are important virulence factors that allow binding of the bacteria to specific receptors on epithelial cells of the urinary tract. The two adhesins most commonly associated with UTI are type 1 fimbriae, and pyelonephritisassociated pili (Pap) and Pap-related fimbriae (Prf); the last two are collectively termed P fimbriae in this study. Type 1 fimbriae mediate binding to a-D-mannose-containing receptors and extracellular matrix components, whereas P fimbriae bind to glycoreceptors containing the aGal(1-4)bGal moiety (Lindberg et al., 1984). Although type 1 fimbriae are common to the majority of E. coli isolates, the FimH adhesin has been shown to be important in a mouse model of UTI, and a degranulation response to the fimbriae is asso...

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“…Lrp, for instance, slightly affects the transcription of both fimB and fimE. Additionally, it also binds with high affinity within the fim switch, and this binding stimulates recombination in both directions (Gally et al, 1994). In the case of H-NS, it has been shown that H-NS is a repressor of the FimB recombinase, but there is evidence that this regulation is not the sole cause of the increased DNA flipping observed in hns mutant backgrounds (Donato et al, 1997).…”

Section: Control Of Fimbrial Expressionmentioning

confidence: 99%

“…FimE, on the other hand, causes only switching from phase-ON to phase-OFF (Blomfield et al, 1991;Gally et al, 1996). In addition to the fim recombinases, efficient inversion of the fim switch requires the accessory proteins integration host factor (IHF) and leucine-responsive regulatory protein (Lrp) (Blomfield et al, 1993(Blomfield et al, , 1997Dorman & Higgins, 1987;Gally et al, 1994). The histone-like nucleoid-structuring protein (H-NS) is also involved in the recombination event (Donato et al, 1997;O'Gara and Dorman, 2000;Olsen & Klemm, 1994).…”

Section: Introductionmentioning

confidence: 99%

Regulation of type 1 fimbriae synthesis and biofilm formation by the transcriptional regulator LrhA of Escherichia coli

et al. 2005

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Type 1 fimbriae of Escherichia coli facilitate attachment to the host mucosa and promote biofilm formation on abiotic surfaces. The transcriptional regulator LrhA, which is known as a repressor of flagellar, motility and chemotaxis genes, regulates biofilm formation and expression of type 1 fimbriae. Whole-genome expression profiling revealed that inactivation of lrhA results in an increased expression of structural components of type 1 fimbriae. In vitro, LrhA bound to the promoter regions of the two fim recombinases (FimB and FimE) that catalyse the inversion of the fimA promoter, and to the invertible element itself. Translational lacZ fusions with these genes and quantification of fimE transcript levels by real-time PCR showed that LrhA influences type 1 fimbrial phase variation, primarily via activation of FimE, which is required for the ON-to-OFF transition of the fim switch. Enhanced type 1 fimbrial expression as a result of lrhA disruption was confirmed by mannose-sensitive agglutination of yeast cells. Biofilm formation was stimulated by lrhA inactivation and completely suppressed upon LrhA overproduction. The effects of LrhA on biofilm formation were exerted via the changed levels of surface molecules, most probably both flagella and type 1 fimbriae. Together, the data show a role for LrhA as a repressor of type 1 fimbrial expression, and thus as a regulator of the initial stages of biofilm development and, presumably, bacterial adherence to epithelial host cells also.

show abstract

The leucine-responsive regulatory protein binds to the fim switch to control phase variation of type 1 fimbrial expression in Escherichia coli K-12

Cited by 99 publications

References 23 publications

Regulation of Expression of Uropathogenic Escherichia coli Nonfimbrial Adhesin TosA by PapB Homolog TosR in Conjunction with H-NS and Lrp

Regulation of Expression of Uropathogenic Escherichia coli Nonfimbrial Adhesin TosA by PapB Homolog TosR in Conjunction with H-NS and Lrp

Demonstration of regulatory cross-talk between P fimbriae and type 1 fimbriae in uropathogenic Escherichia coli

Regulation of type 1 fimbriae synthesis and biofilm formation by the transcriptional regulator LrhA of Escherichia coli

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