Immunoelectron microscopic analysis of elongation of type 1 fimbriae in Escherichia coli

Lowe, Michael; Holt, Stanley C.; Eisenstein, B I

doi:10.1128/jb.169.1.157-163.1987

Cited by 54 publications

(21 citation statements)

References 25 publications

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“…A type 1 fimbria is a 7-nm-wide, approximately 1-m-long, rod-shaped structure consisting of four different components that are added to the base of the growing organelle (22). The bulk of the structure consists of about 1,000 copies of the major subunit protein, FimA, polymerized into a right-handed helical structure, but small quantities of the minor components, FimF, FimG, and FimH are also present (14,19).…”

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confidence: 99%

Biofilm Formation in a Hydrodynamic Environment by Novel FimH Variants and Ramifications for Virulence

2001

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Type 1 fimbriae are surface-located adhesion organelles of Escherichia coli that are directly associated with virulence of the urinary tract. They mediate D-mannose-sensitive binding to different host surfaces by way of the minor fimbrial component FimH. Naturally occurring variants of FimH that bind strongly to terminally exposed monomannose residues have been associated with a pathogenicity-adaptive phenotype that enhances E. coli colonization of extraintestinal locations such as the urinary tract. The FimH adhesin also promotes biofilm formation in a mannose-inhibitable manner on abiotic surfaces under static growth conditions. In this study, we used random mutagenesis combined with a novel selection-enrichment technique to specifically identify mutations in the FimH adhesin that confer on E. coli the ability to form biofilms under hydrodynamic flow (HDF) conditions. We identified three FimH variants from our mutant library that could mediate an HDF biofilm formation phenotype to various degrees. This phenotype was induced by the cumulative effect of multiple changes throughout the receptor-binding region of the protein. Two of the HDF biofilm-forming FimH variants were insensitive to mannose inhibition and represent novel phenotypes not previously identified in naturally occurring isolates. Characterization of our enriched clones revealed some similarities to amino acid alterations that occur in urinary tract infection (UTI) strains. Subsequent screening of a selection of UTI FimH variants demonstrated that they too could promote biofilm formation on abiotic surfaces under HDF conditions. Interestingly, the same correlation was not observed for commensal FimH variants. FimH is a multifaceted protein prone to rapid microevolution. In addition to its previously documented roles in adherence and invasion, we have now demonstrated its function in biofilm formation on abiotic surfaces subjected to HDF conditions. The study indicates that UTI FimH variants possess adaptations that enhance biofilm formation and suggests a novel role for FimH in UTIs associated with medical implants such as catheters.

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confidence: 99%

Biofilm Formation in a Hydrodynamic Environment by Novel FimH Variants and Ramifications for Virulence

2001

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“…A single type 1 fimbria is a 7-nm-wide, approximately 1-m-long rod-shaped structure consisting of four different components that are added to the base of the growing organelle (21). The bulk of the structure is made up of about 1,000 copies of the major subunit protein, FimA, polymerized into a right-handed helical structure, but small quantities of the minor components, FimF, FimG, and FimH, are also present (12,18).…”

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confidence: 99%

Functional Flexibility of the FimH Adhesin: Insights from a Random Mutant Library

2000

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Type 1 fimbriae are surface organelles of Escherichia coli which mediate D-mannose-sensitive binding to different host surfaces. This binding is conferred by the minor fimbrial component FimH. Naturally occurring variants of the FimH protein have been selected in nature for their ability to recognize specific receptor targets. In particular, variants that bind strongly to terminally exposed monomannose residues have been associated with a pathogenicity-adaptive phenotype that enhances E. coli colonization of extraintestinal locations such as the urinary bladder. In this study we have used random mutagenesis to specifically identify nonselective mutations in the FimH adhesin which modify its binding phenotype. Isogenic E. coli clones expressing FimH variants were tested for their ability to bind yeast cells and model glycoproteins that contain oligosaccharide moieties rich in either terminal monomannose, oligomannose, or nonmannose residues. Both the monomannose-and the oligomannose-binding capacity of type 1 fimbriae could be altered by minor amino acid changes in the FimH protein. The monomannose-binding phenotype was particularly sensitive to changes, with extensive differences in binding being observed in comparison to wild-type FimH levels. Different structural alterations were able to cause similar functional changes in FimH, suggesting a high degree of flexibility to target recognition by this adhesin. Alteration of residue P49 of the mature FimH protein, which occurs within the recently elucidated carbohydrate-binding pocket of FimH, completely abolished its function. Amino acid changes that increased the binding capacity of FimH were located outside receptor-interacting residues, indicating that functional changes relevant to pathogenicity are likely to be due to conformational changes of the adhesin.

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“…However, upon longer incubation on the filters (6 h; also corresponds with maximum transfer efficiencies), cells harbored only one or two long filamentous structures, which were always in attachment with other cells. Variation in pilus length with time has been previously observed, especially in the pathogenic E. coli (11,29,36,37), where changing pilus lengths are associated with bacterial adherence and aggregation. We speculate that, at the onset of the mating period, Tet element-harboring cells express these piluslike structures all over the cell surface but that, upon contact with another cell, only those structures involved in attachment remain, while others retract.…”

Section: Discussionmentioning

confidence: 99%

Isolation and Characterization of BTF-37: Chromosomal DNA Captured from Bacteroides fragilis That Confers Self-Transferability and Expresses a Pilus-Like Structure in Bacteroides spp. and Escherichia coli

Vedantam

Hecht

2002

J Bacteriol

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We report the isolation and preliminary characterization of BTF-37, a new 52-kb transfer factor isolated from Bacteroides fragilis clinical isolate LV23. BTF-37 was obtained by the capture of new DNA in the nonmobilizable Bacteroides-Escherichia coli shuttle vector pGAT400⌬BglII using a functional assay. BTF-37 is self-transferable within and from Bacteroides and also self-transfers in E. coli. Partial DNA sequencing, colony hybridization, and PCR revealed the presence of Tet element-specific sequences in BTF-37. In addition, Tn5520, a small mobilizable transposon that we described previously (G. Vedantam, T. J. Novicki, and D. W. Hecht, J. Bacteriol. 181:2564-2571, 1999), was also coisolated within BTF-37. Scanning and transmission electron microscopy of Tet element-containing Bacteroides spp. and BTF-37-harboring Bacteroides and E. coli strains revealed the presence of pilus-like cell surface structures. These structures were visualized in Bacteroides spp. only when BTF-37 and Tet element strains were induced with subinhibitory concentrations of tetracycline and resembled those encoded by E. coli broad-host-range plasmids. We conclude that we have captured a new, self-transferable transfer factor from B. fragilis LV23 and that this new factor encodes a tetracycline-inducible Bacteroides sp. conjugation apparatus.Horizontal DNA transfer by conjugation is widespread in the bacterial world and has been responsible in part for the dissemination of antibiotic resistance genes (22, 59). Conjugation between bacterial genera and species and also interkingdom conjugation (bacteria to yeast and bacteria to plants [6)]) have been shown to occur. While mobile genetic elements such as plasmids and transposons are most frequently transferred by conjugation, segments of chromosomal DNA can also be transferred by this process (17,31).Members of the genus Bacteroides are obligate, gram-negative, colonic anaerobes. Bacteroides spp. possess a plethora of mobile transfer factors, many of which harbor antibiotic resistance genes. These factors have been shown to transfer within and from Bacteroides, thus implicating these organisms as reservoirs of antibiotic resistance (A. A. Salyers, Letter, ASM News 65:459-460, 1999).DNA transfer by conjugation involves two major sets of processes: initiation and mating apparatus formation. Initiation results in the formation of a relaxosome, an ordered assembly of proteins that nick the DNA to be transferred in a site-and strand-specific manner (32,44,45,65). This nicked DNA is unwound and transmitted with 5Ј-3Ј polarity from the donor to the recipient. In Escherichia coli, the passage from donor to recipient is thought to occur through a specialized membrane-traversing channel. The channel and all accessory proteins required for mating pair stabilization, cell-cell contact, surface and entry exclusion, and DNA transfer are collectively referred to as the mating apparatus. For the E. coli F and RP4 plasmids and the Agrobacterium tumefaciens Ti plasmid, it is thought that at least 21, 12, and 1...

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Immunoelectron microscopic analysis of elongation of type 1 fimbriae in Escherichia coli

Cited by 54 publications

References 25 publications

Biofilm Formation in a Hydrodynamic Environment by Novel FimH Variants and Ramifications for Virulence

Biofilm Formation in a Hydrodynamic Environment by Novel FimH Variants and Ramifications for Virulence

Functional Flexibility of the FimH Adhesin: Insights from a Random Mutant Library

Isolation and Characterization of BTF-37: Chromosomal DNA Captured from Bacteroides fragilis That Confers Self-Transferability and Expresses a Pilus-Like Structure in Bacteroides spp. and Escherichia coli

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