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.

The fimbriae activator MatA switches off motility in Escherichia coli by repression of the flagellar master operon flhDC

“…Constitutive expression of type 1 fimbriae, an essential virulence factor in UTIs (Connell et al, 1996), has been shown to decrease motility of UPEC (Bryan et al, 2006;Lane et al, 2007a), partially due to the abundance of fimbrial structures at the cell surface (Lane et al, 2007a). Subsequent screening of factors that participate in a decreased-motility phenotype identified four transcriptional regulators, LrhA, Lrp, SlyA and P fimbriae protein PapX, that partially restore motility without affecting type 1 fimbriae expression (Simms & Mobley, 2008a). PapX binds to a 29 bp DNA region located 410 bp upstream of the flhD start codon, and when overexpressed, PapX decreases motility of the UPEC strain CFT073 by repressing flhDC transcription.…”

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

“…A phage transductant of the original tosR deletion mutation (10) was unmarked using the FLP recombinase as previously described (10). The ⌬hns ⌬lrp CFT073 strain was engineered through phage-mediated transduction of a previous CFT073 ⌬lrp mutation (19) into a previous lambda Red-engineered CFT073 ⌬hns mutant unmarked as described above. Transductants were selected for on lysogeny broth (LB) agar (10 g/liter tryptone, 5 g/liter yeast extract, 0.5 g/liter NaCl, 15 g/liter agar) containing kanamycin (25 g/ml).…”

“…The tos operon, in addition to tosA and predicted cognate secretion system genes tosCBD, also contains the regulatory genes tosR, tosE, and tosF (9,10). TosE and TosF together suppress motility (10), a feature also found in other adhesin operon regulators (19)(20)(21). TosR, a member of the PapB family, is a negative regulator of the tos operon (10).…”

The role of bacterial virulence factors in the clinical course of urinary tract infections

“…Flagella have been proposed to provide a selective advantage in the early colonization of the urinary tract [33] and flagellum-driven motility is proposed to enhance bacterial dissemination to the upper urinary tract and facilitate bacterial spread to sites more advantageous for colonization [76]. Sp10 was a 100% motile re-isolate, whereas R15-2 contained a mixture of motile and non-motile cells.…”