Regulation of type 1 pili expression as exemplified by Escherichia coli strain M17

Studies of E. coli strain M17 colibacterin and its derivatives showed that fimH gene regulates morphological characteristics of type 1 fimbria and cell piliation on the whole. Gene fimH has a negative effect and decreased the percentage of piliated cells in the population and piliation of individual cells, which does not agree with its role of a positive regulator

Escherichia coli strain M17: Analysis of adhesive phenotype as a factor of host colonization and/or pathogenicity

FimH adhesins M1L and M1H are differently adapted to colonization of primary normal and secondary pathological niches of human E. coli. The M-L phenotype is typical and optimal for intestinal E. coli, while M-H phenotype predominates among pathogenic strains and is undesirable for the eubiotic intestinal E. coli strain M17

Molecular genetic analysis of Escherichia coli type I adhesins

Protein FimH is an adhesive terminal subunit of Escherichia coli type I pili. The content of FimH on the surface of a bacterial cell does not directly depend on FimH expression, but is limited by expression of other fim cluster genes encoding structural subunits and proteins responsible for assembly of pili. Piline domain, a component of FimH, cannot incorporate into the fimbria independently, without lectin domain. It seems that fimbriae containing only piline domain are not formed because of inability of the piline domain to initiate the process of assembly. © Springer Science+Business Media, Inc. 2006

Escherichia coli strain M17: Analysis of adhesive phenotype as a factor of host colonization and/or pathogenicity

FimH adhesins M1L and M1H are differently adapted to colonization of primary normal and secondary pathological niches of human E. coli. The M-L phenotype is typical and optimal for intestinal E. coli, while M-H phenotype predominates among pathogenic strains and is undesirable for the eubiotic intestinal E. coli strain M17

Regulation of type 1 pili expression as exemplified by Escherichia coli strain M17

Studies of E. coli strain M17 colibacterin and its derivatives showed that fimH gene regulates morphological characteristics of type 1 fimbria and cell piliation on the whole. Gene fimH has a negative effect and decreased the percentage of piliated cells in the population and piliation of individual cells, which does not agree with its role of a positive regulator

Molecular genetic analysis of Escherichia coli type I adhesins

Protein FimH is an adhesive terminal subunit of Escherichia coli type I pili. The content of FimH on the surface of a bacterial cell does not directly depend on FimH expression, but is limited by expression of other fim cluster genes encoding structural subunits and proteins responsible for assembly of pili. Piline domain, a component of FimH, cannot incorporate into the fimbria independently, without lectin domain. It seems that fimbriae containing only piline domain are not formed because of inability of the piline domain to initiate the process of assembly. © Springer Science+Business Media, Inc. 2006

Diversity of the Escherichia coli type 1 Fimbrial lectin: Differential binding to mannosides and uroepithelial cells

Type 1 fimbriae are the most common adhesive organelles of Escherichia cell. Because of their virtual ubiquity, previous epidemiological studies have not found a correlation between the presence of type 1 fimbriae and urinary tract infections (UTIs). Recently it has become clear that type 1 fimbriae exhibit several different phenotypes, due to allelic variation of the gene for the lectin subunit, FimH, and that these phenotypes are differentially distributed among fecal and UTI isolates. In this study, we have analyzed in more detail the ability of isogenic, recombinant strains of E. coli expressing fimH genes of the predominant fecal and UTI phenotypes to adhere to glycoproteins and to uroepithelial cells. Evidence was obtained to indicate that type 1 fimbriae differ in their ability to recognize various mannosides, utilizing at least two different mechanisms. All FimH subunits studied to date are capable of mediating adhesion via trimannosyl residues, but only certain variants are capable of mediating high levels of adhesion via monomannosyl residues. The ability of the FimH lectins to interact with monomannosyl residues strongly correlates with their ability to mediate E. coli adhesion to uroepithelial cells. In this way, it would be possible for certain phenotypic variants of type 1 fimbriae to contribute more than others to virulence of E. coli in the urinary tract

Differential stability and trade-off effects of pathoadaptive mutations in the Escherichia coli FimH adhesin

FimH is the tip adhesin of mannose-specific type 1 fimbriae of Escherichia coli, which are critical to the pathogenesis of urinary tract infections. Point FimH mutations increasing monomannose (1M)-specific uroepithelial adhesion are commonly found in uropathogenic strains of E. coli. Here, we demonstrate the emergence of a mixed population of clonally identical E. coli strains in the urine of a patient with acute cystitis, where half of the isolates carried a glycine-to-arginine substitution at position 66 of the mature FimH. The R66 mutation induced an unusually strong 1M-binding phenotype and a 20-fold advantage in mouse bladder colonization. However, E. coli strains carrying FimH-R66, but not the parental FimH-G66, had disappeared from the patient's rectal and urine samples collected from 29 to 44 days later, demonstrating within-host instability of the R66 mutation. No FimH variants with R66 were identified in a large (>600 strains) sequence database of fimH-positive E. coli strains. However, several strains carrying genes encoding FimH with either S66 or C66 mutations appeared to be relatively stable in the E. coli population. Relative to FimH-R66, the FimH-S66 and FimH-C66 variants mediated only moderate increases in 1M binding but preserved the ability to enhance binding under flow-induced shear conditions. In contrast, FimH-R66 completely lost shear-enhanced binding properties, with bacterial adhesion being inhibited by shear forces and lacking a rolling mode of binding. These functional trade-offs may determine the natural populational instability of this mutation or other pathoadaptive FimH mutations that confer dramatic increases in 1M binding strength. Copyright © 2007, American Society for Microbiology. All Rights Reserved

Differential stability and trade-off effects of pathoadaptive mutations in the Escherichia coli FimH adhesin

FimH is the tip adhesin of mannose-specific type 1 fimbriae of Escherichia coli, which are critical to the pathogenesis of urinary tract infections. Point FimH mutations increasing monomannose (1M)-specific uroepithelial adhesion are commonly found in uropathogenic strains of E. coli. Here, we demonstrate the emergence of a mixed population of clonally identical E. coli strains in the urine of a patient with acute cystitis, where half of the isolates carried a glycine-to-arginine substitution at position 66 of the mature FimH. The R66 mutation induced an unusually strong 1M-binding phenotype and a 20-fold advantage in mouse bladder colonization. However, E. coli strains carrying FimH-R66, but not the parental FimH-G66, had disappeared from the patient's rectal and urine samples collected from 29 to 44 days later, demonstrating within-host instability of the R66 mutation. No FimH variants with R66 were identified in a large (>600 strains) sequence database of fimH-positive E. coli strains. However, several strains carrying genes encoding FimH with either S66 or C66 mutations appeared to be relatively stable in the E. coli population. Relative to FimH-R66, the FimH-S66 and FimH-C66 variants mediated only moderate increases in 1M binding but preserved the ability to enhance binding under flow-induced shear conditions. In contrast, FimH-R66 completely lost shear-enhanced binding properties, with bacterial adhesion being inhibited by shear forces and lacking a rolling mode of binding. These functional trade-offs may determine the natural populational instability of this mutation or other pathoadaptive FimH mutations that confer dramatic increases in 1M binding strength. Copyright © 2007, American Society for Microbiology. All Rights Reserved