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Coordinate expression of fimbriae in uropathogenic Escherichia coli.

ABSTRACT: Uropathogenic Escherichia coli is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of other adhesins. Type 1 fimbrial phase-locked mutants of E. coli strain CFT073, which harbors genes for numerous adhesins, were employed in this study. CFT073-specific DNA microarray analysis of these strains demonstrates that the expression of type 1 fimbriae coordinately affects the expression of P fimbriae in an inverse manner. This represents evidence for direct communication between genes relating to pathogenesis, perhaps to aid the sequential occupation of different urinary tract tissues. While the role of type 1 fimbriae during infection has been clear, the role of P fimbriae must be further defined to assert the relevance of coordinated regulation in vivo. Therefore, we examined the ability of P fimbrial isogenic mutants, constructed in a type 1 fimbrial-negative background, to compete in the murine urinary tract over a period of 168 h. No differences in the colonization of these mutants were observed. However, comparison of these results with previous studies suggests that inversely coordinated expression of adhesin gene clusters does occur in vivo. Interestingly, the mutant that was incapable of expressing either type 1 or P fimbriae compensated by synthesizing F1C fimbriae.

SUBMITTER: Snyder JA

PROVIDER: S-EPMC1273908 | biostudies-literature | 2005 Nov

REPOSITORIES: biostudies-literature

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Coordinate expression of fimbriae in uropathogenic Escherichia coli.

Snyder Jennifer A JA Haugen Brian J BJ Lockatell C Virginia CV Maroncle Nathalie N Hagan Erin C EC Johnson David E DE Welch Rodney A RA Mobley Harry L T HL

Infection and immunity 20051101 11

Uropathogenic Escherichia coli is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of o ...[more]

PMID: 16239562

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Project description:F1C fimbriae are correlated with uropathogenic Escherichia coli strains. Although F1C fimbriae mediate binding to kidney tubular cells, their receptor is not known. In this paper, we demonstrate for the first time specific carbohydrate residues as receptor structure for F1C-fimbria-expressing E. coli. The binding of the F1C fimbriated recombinant E. coli strain HB101(pPIL110-54) and purified F1C fimbriae to reference glycolipids of different carbohydrate compositions was evaluated by using thin-layer chromatography (TLC) overlay and solid-phase binding assays. TLC fimbrial overlay analysis revealed the binding ability of purified F1C fimbriae only to glucosylceramide (GlcCer), beta1-linked galactosylceramide 2 (GalCer2) with nonhydroxy fatty acids, lactosylceramide, globotriaosylceramide, paragloboside (nLc(4)Cer), lactotriaosylceramide, gangliotriaosylceramide (asialo-GM(2) [GgO(3)Cer]) and gangliotetraosylceramide (asialo-GM(1) [GgO(4)Cer]). The binding of purified F1C fimbriae as well as F1C fimbriated recombinant E. coli strain HB101(pPIL110-54) was optimal to microtiter plates coated with asialo-GM(2) (GgO(3)Cer). The bacterial interaction with asialo-GM(1) (GgO(4)Cer) and asialo-GM(2) (GgO(3)Cer) was strongly inhibited only by disaccharide GalNAcbeta1-4Galbeta linked to bovine serum albumin. We observed no binding to globotetraosylceramide or Forssman antigen (Gb(5)Cer) glycosphingolipids or to sialic-acid-containing gangliosides. It was demonstrated that the presence of a GalCer or GlcCer residue alone is not sufficient for optimal binding, and additional carbohydrate residues are required for high-affinity adherence. Indeed, the binding efficiency of F1C fimbriated recombinant bacteria increased by 19-fold when disaccharide sequence GalNAcbeta1-4Galbeta is linked to glucosylceramide as in asialo-GM(2) (GgO(3)Cer). Thus, it is suggested that the disaccharide sequence GalNAcbeta1-4Galbeta of asialo-GM(2) (GgO(3)Cer) which is positioned internally in asialo-GM(1) (GgO(4)Cer) is the high-affinity binding epitope for the F1C fimbriae of uropathogenic E. coli.

Project description:Type 1 fimbriae are a crucial factor for the virulence of uropathogenic Escherichia coli during the first steps of infection by mediating adhesion to epithelial cells. They are also required for the consequent colonization of the tissues and for invasion of the uroepithelium. Here, we studied the role of the specialized signal transduction system CRP-cAMP in the regulation of type 1 fimbriation. Although initially discovered by regulating carbohydrate metabolism, the CRP-cAMP complex controls a major regulatory network in Gram-negative bacteria, including a broad subset of genes spread into different functional categories of the cell. Our results indicate that CRP-cAMP plays a dual role in type 1 fimbriation, affecting both the phase variation process and fimA promoter activity, with an overall repressive outcome on fimbriation. The dissection of the regulatory pathway let us conclude that CRP-cAMP negatively affects FimB-mediated recombination by an indirect mechanism that requires DNA gyrase activity. Moreover, the underlying studies revealed that CRP-cAMP controls the expression of another global regulator in Gram-negative bacteria, the leucine-responsive protein Lrp. CRP-cAMP-mediated repression is limiting the switch from the non-fimbriated to the fimbriated state. Consistently, a drop in the intracellular concentration of cAMP due to altered physiological conditions (e.g. growth in presence of glucose) increases the percentage of fimbriated cells in the bacterial population. We also provide evidence that the repression of type 1 fimbriae by CRP-cAMP occurs during fast growth conditions (logarithmic phase) and is alleviated during slow growth (stationary phase), which is consistent with an involvement of type 1 fimbriae in the adaptation to stress conditions by promoting biofilm growth or entry into host cells. Our work suggests that the metabolic sensor CRP-cAMP plays a role in coupling the expression of type 1 fimbriae to environmental conditions, thereby also affecting subsequent attachment and colonization of host tissues.

Dataset Information

Coordinate expression of fimbriae in uropathogenic Escherichia coli.

Publications

Coordinate expression of fimbriae in uropathogenic Escherichia coli.

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