Functional analysis of the minor subunits of S fimbrial adhesin (SfaI) in pathogenic Escherichia coli

Abstract

S fimbrial adhesins I and II (SfaI and II), produced by extraintestinal Escherichia coli pathogens that cause urinary tract infections (UTI) and newborn meningitis (NBM), respectively, mediate bacterial adherence to sialic acid-containing glycoprotein receptors present on host epithelial cells and extracellular matrix. The S fimbrial adhesin complexes consist of four proteins: SfaI-A, the major subunit protein and the minor subunit proteins SfaI-G, SfaI-S and SfaI-H. Sialic acid-specific binding is mediated by the minor subunit protein SfaI-S. In order to determine whether the minor subunit proteins SfaI-G, -S and -H play a role in the modulation of adherence and the degree of fimbriation, a trans-complementation system was developed. A non-adhesive E. coli K-12 derivative, harbouring the sfaI-A gene but lacking sfaI-G, -S and -H, was transformed with sfaI-G, -S or -H. Only SfaI-S was able to increase the degree of fimbriation and to confer adhesion properties on the recombinant E. coli K-12 strains. Amino acid residues in SfaI-S that are involved in modulation of fimbriation as well as in receptor recognition were localized by random and site-directed mutagenesis.

Novel Type of Fimbriae Encoded by the Large Plasmid of Sorbitol-Fermenting Enterohemorrhagic Escherichia coli O157:H −

“…One of the best understood mechanisms of adherence is that mediated by rod-shaped proteinaceous appendages of the bacterial surface called fimbriae or pili. Well-studied adhesion systems of pathogenic bacteria are the S-fimbria superfamily (30,31) and the P (pyelonephritis-associated)-fimbriae of uropathogenic Escherichia coli. The latter are composed of a thin tip fibrillum (2 nm in diameter) carrying the adhesin at its distal end and joined at its proximal end to a more rigid, 7-nm-diameter pilus rod (10).…”

New Fimbrial Gene Cluster of S-Fimbrial Adhesin Family

“…For example, AC/I fimbriae do not agglutinate red blood cells, in contrast to SfaS-I and SfaS-II, which are identical and responsible for the sialic acid-specific binding of the S-fimbriae. Furthermore, while AC/I fimbriae preferentially bind avian tracheal cells, F1C fimbriae attach to uroepithelial cells of human origin (16,29).…”

“…These fimbriae, named Sfa-II fimbriae, differ from Sfa-I fimbriae in the major subunit and in two minor subunits. However, they also bind sialylgalactosides, and their gene coding for the fimbrial adhesin, sfaS, is identical to the equivalent gene of the sfa I cluster from UTI bacteria (11,16).…”

“…These proteins are preferentially found at the fimbrial tip, and they play an important role in determining adhesin specificity (16,46).…”

A Salmonella fim Homologue in Citrobacter freundii Mediates Invasion In Vitro and Crossing of the Blood-Brain Barrier in the Rat Pup Model

“…In order to determine whether sfaI, sfaII, sfr, foc, and fim determinant-carrying recombinant bacteria and control strain HB101, harboring the plasmid vector pBR322, are fimbriated or not, enzyme-linked immunosorbent assays (ELISA) were performed (25). Overnight bacterial cultures were centrifuged, and bacterial pellets were resuspended in a carbonate buffer (pH 9.5) to a concentration of 10 9 CFU/ml.…”