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Multiple genes repress motility in uropathogenic Escherichia coli constitutively expressing type 1 fimbriae.

ABSTRACT: Two surface organelles of uropathogenic Escherichia coli (UPEC), flagella and type 1 fimbriae, are critical for colonization of the urinary tract but mediate opposite actions. Flagella propel bacteria through urine and along mucus layers, while type 1 fimbriae allow bacteria to adhere to specific receptors present on uroepithelial cells. Constitutive expression of type 1 fimbriae leads to repression of motility and chemotaxis in UPEC strain CFT073, suggesting that UPEC may coordinately regulate motility and adherence. To identify genes involved in this regulation of motility by type 1 fimbriae, transposon mutagenesis was performed on a phase-locked type 1 fimbrial ON variant of strain CFT073 (CFT073 fim L-ON), followed by a screen for restoration of motility in soft agar. Functions of the genes identified included attachment, metabolism, transport, DNA mismatch repair, and transcriptional regulation, and a number of genes had hypothetical function. Isogenic deletion mutants of these genes were also constructed in CFT073 fim L-ON. Motility was partially restored in six of these mutants, including complementable mutations in four genes encoding known transcriptional regulators, lrhA, lrp, slyA, and papX; a mismatch repair gene, mutS; and one hypothetical gene, ydiV. Type 1 fimbrial expression in these mutants was unaltered, and the majority of these mutants expressed larger amounts of flagellin than the fim L-ON parental strain. Our results indicate that repression of motility in CFT073 fim L-ON is not solely due to the constitutive expression of type 1 fimbriae on the surfaces of the bacteria and that multiple genes may contribute to this repression.

SUBMITTER: Simms AN

PROVIDER: S-EPMC2395009 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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.

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Multiple genes repress motility in uropathogenic Escherichia coli constitutively expressing type 1 fimbriae.

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