Positive selection identifies an in vivo role for FimH during urinary tract infection in addition to mannose binding

Abstract

FimH, the type 1 pilus adhesin of uropathogenic Escherichia coli (UPEC), contains a receptor-binding domain with an acidic binding pocket specific for mannose. The fim operon, and thus type 1 pilus production, is under transcriptional control via phase variation of an invertible promoter element. FimH is critical during urinary tract infection for mediating colonization and invasion of the bladder epithelium and establishment of intracellular bacterial communities (IBCs). In silico analysis of FimH gene sequences from 279 E. coli strains identified specific amino acids evolving under positive selection outside of its mannose-binding pocket. Mutating two of these residues (A27V/V163A) had no effect on phase variation, pilus assembly, or mannose binding in vitro. However, compared to wild-type, this double mutant strain exhibited a 10,000-fold reduction in mouse bladder colonization 24 h after inoculation and was unable to form IBCs even though it bound normally to mannosylated receptors in the urothelium. In contrast, the single A62S mutation altered phase variation, reducing the proportion of piliated cells, reduced mannose binding 8-fold, and decreased bladder colonization 30-fold in vivo compared to wild-type. A phase-locked ON A62S mutant restored virulence to wild-type levels even though in vitro mannose binding remained impaired. Thus, positive selection analysis of FimH has separated mannose binding from in vivo fitness, suggesting that IBC formation is critical for successful infection of the mammalian bladder, providing support for more general use of in silico positive selection analysis to define the molecular underpinnings of bacterial pathogenesis.type 1 pili ͉ uropathogenic Escherichia coli

Urinary tract infection drives genome instability in uropathogenicEscherichia coliand necessitates translesion synthesis DNA polymerase IV for virulence

“…FimH of UPEC has an increased affinity for monomannosylations present on apical proteins of the urinary tract such as uroplakins while FimH of commensal bacteria have greater affinity for tri-mannosylations more likely to be present in nonurinary tract niches. 13,14,51 yield low fidelity synthesis during processing undamaged and damaged templates due to that lack of exonuclease functions. 24 In addition to evaluating the potential roles of Pol IV and Pol V in genome instability and fitness of UPEC during UTI, we considered the possibility that additional homologs may be present and thus responsible for any observed phenotypes.…”

“…Alternatively, repair of these lesions and errors may require low fidelity bypass synthesis, resulting in mutations, which in turn may promote selective changes such as increased virulence or antibiotic resistance. 13,14 The most important components of mutational level control entail critical DNA synthesis and DNA repair processes are DNA polymerases. There are five known E. coli polymerases where the ©2 0 1 1 L a n d e s B i o s c i e n c e .…”

What does it take to stick around?

“…8 UPEC harbor numerous CUP pili systems, the differential expression of which is thought to facilitate colonization of different niches. [9][10][11][12][13] Type 1 pili mediate adherence largely via the FimH tip adhesin, which recognizes and binds mannosylated moieties on biotic and abiotic surfaces. 4,6,[14][15][16][17][18][19][20] Within the host, FimH mediates UPEC binding to the bladder epithelium and is also required for proper formation of biofilm-like intracellular bacterial communities (IBCs) within bladder epithelial cells.…”

Caracterização de Escherichia coli uropatogênicas isoladas de crianças com infecção urinária.

“…Ela possui afinidade a oligossacarídeos do tipo manose (KROGFELT et al, 1990) e em UPEC é essencial para a adesão ao epitélio do trato urinário (CHEN et al, 2009). Essa fímbria é constituída por um filamento protéico de aproximadamente 5 nm de espessura e 1 a 2µm de comprimento, codificado pelo operon fim, composto pelos genes: fimA, fimB, fimC, fimD, fimE, fimF, fimG, fimH e fimL (MOL;OUDEGA, 1996), responsáveis pela expressão e montagem do filamento via chaperonina-usher.…”

“…(HULTGREN et al, 1991). A proteína codificada pelo gene fimA corresponde a maior subunidade fimbrial, enquanto o gene fimH codifica a menor subunidade da fímbria, presente na extremidade da estrutura fimbrial e responsável pela sua aderência (CHEN et al, 2009). …”