
Ian C BlomfieldUniversity of Kent | KENT · School of Biosciences
Ian C Blomfield
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Publications (35)
Sialic acid and N-acetylglucosamine Regulate type 1 Fimbriae Synthesis, Page 1 of 2
Abstract
Type 1 fimbriae of E. coli, a chaperon-usher bacterial adhesin, are synthesized by the majority of strains of the bacterium. Although frequently produced by commensal strains, the adhesin is nevertheless a virulence factor in Extraintestinal Pathogenic E....
Fimbria-mediated interaction with the host elicits both innate and adaptive immune responses, and thus their expression may not always be beneficial in vivo. Furthermore, the metabolic drain of producing fimbriae is significant. It is not surprising, therefore, to find that fimbrial production in Escherichia coli and Salmonella enterica is under ex...
The phase variation (reversible on-off switching) of the type 1 fimbrial adhesin of Escherichia coli involves a DNA inversion catalyzed by FimB (switching in either direction) or FimE (on-to-off switching). Here, we demonstrate
that RfaH activates expression of a FimB-LacZ protein fusion while having a modest inhibitory effect on a comparable fimB-...
We have demonstrated that SlyA activates fimB expression and hence type 1 fimbriation, a virulence factor in Escherichia coli. SlyA is shown to bind to two operator sites (OSA1 and OSA2), situated between 194 and 167 base pairs upstream of the fimB transcriptional start site. fimB expression is derepressed in an hns mutant and diminished by a slyA...
Fimbriae are structures in Escherichia coli, the expression of which is controlled by the fim operon. Understanding this expression is important because the fimbriae are important virulence factors.
This expression can be studied using targeted mutations to the DNA, which can be used to disable binding or transcription
of a protein. However, this...
The defining feature of bacterial phase variation is a stochastic 'all-or-nothing' switching in gene expression. However, direct observations of these rare switching events have so far been lacking, obscuring possible correlations between switching events themselves, and between switching and other cellular events, such as division and DNA replicat...
Global transcriptional analysis of Candida albicans exposed to elevated ambient CO(2) revealed a statistically significant differential regulation of 14 genes. Subsequent RNA hybridisation analysis of one gene, HSP12, confirmed CO(2)-regulation via a cAMP-dependent mechanism. Additionally, Northern analyses and gel mobility shift assays demonstrate...
This article reports on experimental evidence that an Escherichia coli nanR mutant shows inhibited growth in N-acetylneuraminic acid. This effect is prevented when inocula are grown in an excess of glucose, but not in an excess of glycerol. The nanATEK operon is controlled by catabolite repression, suggesting that diminished expression of the nanAT...
FimB and FimE are site-specific recombinases, part of the lambda integrase family, and invert a 314 bp DNA switch that controls the expression of type 1 fimbriae in Escherichia coli. FimB and FimE differ in their activity towards the fim switch, with FimB catalysing inversion in both directions in comparison to the higher-frequency but unidirection...
Expression of the FimB recombinase, and hence the OFF-to-ON switching of type 1 fimbriation in Escherichia coli, is inhibited by sialic acid (Neu(5)Ac) and by GlcNAc. NanR (Neu(5)Ac-responsive) and NagC (GlcNAc-6P-responsive) activate fimB expression by binding to operators (O(NR) and O(NC1) respectively) located more than 600 bp upstream of the fi...
The fim system in E. coli controls the expression of type-1 fimbriae. These are hair-like structures that can be used to attach to host cells. Fimbriation is controlled by a mechanism called "orientational control." We present two families of models for orientational control to understand the details of how it works. We find that the main benefits...
Phase variation of type 1 fimbriae of Escherichia coli requires the site-specific recombination of a short invertible element. Inversion is catalyzed by FimB (switching in either direction) or FimE (inversion mainly from on to off) and is influenced by auxiliary factors integration host factor (IHF) and leucine-responsive regulatory protein (Lrp)....
Bacterial-host attachment by means of bacterial adhesins is a key step in host colonization. Phase variation (reversible on-off switching) of the type 1 fimbrial adhesin of Escherichia coli involves a DNA inversion catalyzed by FimB (switching in either direction) or FimE (mainly on-to-off switching). fimB is separated from the divergent yjhATS ope...
The phase variation of type 1 fimbriation in Escherichia coli is controlled by the inversion of a 314 bp element of DNA, determined by FimB (switching in both directions) or FimE (switching from the ON-to-OFF orientation predominantly), and influenced by auxiliary factors IHF, Lrp and H-NS. The fimB gene is separated from the divergently transcribe...
Type 1 fimbria is a proven virulence factor of uropathogenic Escherichia coli (UPEC), causing urinary tract infections. Expression of the fimbria is regulated at the transcriptional level by a promoter situated on an invertible element, which can exist in one of two different orientations. The orientation of the invertible element that allows the e...
Phase-variable expression of type 1 fimbriae is, in part, controlled by site-specific DNA inversion of the fim switch in Escherichia coli. Of the two fim recombinases (FimB and FimE) that catalyse the inversion reaction, FimE exhibits a strong bias for phase switching from the ON to the OFF orientation. The specificity associated with fimE is the r...
The ability of bacterial pathogens to bind to the host mucosa is a critical step in the pathogenesis of many bacterial infections and, for Escherichia coli, a large number of different fimbrial adhesins have been implicated as virulence factors. In this chapter, our current understanding of the regulatory mechanisms that control the expression of t...
The expression of type 1 fimbriae in Escherichia coli is phase variable, with cells switching between fimbriate (ON) and afimbriate (OFF) phases. The phase variation is dependent on the orientation of a 314 bp DNA element (the switch) that undergoes DNA inversion. DNA inversion requires either fimB or fimE, site-specific recombinases that differ in...
During infection of the gastrointestinal tract, salmonellae induce cytokine production and inflammatory responses which are believed to mediate tissue damage in the host. In a previous study, we reported that salmonellae possess the ability to stimulate tumor necrosis factor alpha (TNF-alpha) accumulation in primary human monocytes, as well as in t...
The leucine-responsive regulatory protein (Lrp) is a global regulator that controls the expression of numerous operons in Escherichia coli. Lrp can act as a repressor or as an activator of transcription with its effects being potentiated, repressed or unaffected by the presence of exogenous leucine. The phase variation of type 1 fimbria in E. coli...
Proteus mirabilis, associated with complicated urinary tract infection, expresses mannose-resistant/Proteus-like (MR/P) fimbriae. Expression of these surface structures, which mediate haemagglutination and have a demonstrated role in virulence, undergoes phase variation. By DNA sequence analysis, a 252 bp invertible element was found in the interge...
The site-specific DNA inversion that controls phase variation of type 1 fimbriation in E. coli is catalysed by two recombinases, FimB and FimE. Efficient inversion by either recombinase also requires the leucine-responsive regulatory protein (Lrp). In addition, FimB recombination is stimulated by the integration host factor (IHF). The effect of IHF...
The phase variation of type 1 fimbriae in Escherichia coli is associated with the site-specific inversion of a short DNA element. Recombination at fim requires fimB and fimE, and their products are considered to be the fim recombinases. In this study, FimB and FimE were overproduced and extracts containing the proteins were shown to (i) bind to and...
Phase variation of type 1 fimbriation in Escherichia coli is associated with the site-specific recombination of a 314-bp DNA invertible element. The fim switch directs transcription of fimA, the major fimbrial subunit gene, in one orientation (on) but not the other (off). Switching requires either fimB (on-to-off or off-to-on inversion) or fimE (on...
Expression of type 1 fimbriae in Escherichia coli K-12 is phase variable and associated with the inversion of a short DNA element (switch). The fim switch requires either fimB (on-to-off or off-to-on switching) or fimE (on-to-off switching only) and is affected by the global regulators leucine-responsive regulatory protein (Lrp), integration host f...
The roles of fimB and fimE in the phase-variable expression of type 1 fimbriae in Escherichia coli were examined. A method was developed to study the effects of fimB and fimE on both recombination of the fim invertible element and fimbrial expression. The method used an allelic exchange procedure consisting of two steps. The first step, constructio...
The phase variation of type 1 fimbriation in Escherichia coli is associated with the inversion of a short DNA element. This element (switch) acts in cis to control transcription of fimA, the major fimbrial subunit gene. Thus, fimA is transcribed when the switch is in one orientation (the on orientation) but not the other (the off orientation). The...
We reexamined the influence of fimE, also referred to as hyp, on type 1 fimbriation in Escherichia coli K-12. We found that one strain used previously and extensively in the analysis of type 1 fimbriation, strain CSH50, is in fact a fimE mutant; the fimE gene of CSH50 contains a copy of the insertion sequence IS1. Using a recently described allelic...
Evidence obtained with an improved in vivo assay of fimbrial phase variation in Escherichia coli supported a revised understanding of the roles of fimB and fimE in the site-specific DNA rearrangement with which they are associated. A previously proposed model argued that fimB and fimE play antagonistic, unidirectional roles in regulating the orient...
We have used Southern hybridization analysis to characterize the extent of fim homology in recognized type 1 fimbriae mutants of Escherichia coli K12, including strains HB101, P678-54, and VL584. We have found extensive homology in strain HB101, and confirm that P678-54 lacks the majority of fim DNA. Strain VL584 contains a deletion of the entire f...
To facilitate efficient allelic exchange of genetic information into a wild-type strain background, we improved upon and merged approaches using a temperature-sensitive plasmid and a counter-selectable marker in the chromosome. We first constructed intermediate strains of Escherichia coli K12 in which we replaced wild-type chromosomal sequences, at...