SEARCH · PubMed Health

Results for “Type IV pili”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2001

Direct observation of extension and retraction of type IV pili.

Type IV pili are thin filaments that extend from the poles of a diverse group of bacteria, enabling them to move at speeds of a few tenths of a micrometer per second. They are required for twitching motility, e.g., in Pseudomonas aeruginosa and Neisseria gonorrhoeae, and for social gliding motility in Myxococcus xanthus. Here we report direct observation of extension and retraction of type IV pili in P. aeruginosa. Cells without flagellar filaments were labeled with an amino-specific Cy3 fluorescent dye and were visualized on a quartz slide by total internal reflection microscopy. When pili were attached to a cell and their distal ends were free, they extended or retracted at rates of about 0.5 microm s(-1) (29 degrees C). They also flexed by Brownian motion, exhibiting a persistence length of about 5 microm. Frequently, the distal tip of a filament adsorbed to the substratum and the filament was pulled taut. From the absence of lateral deflections of such filaments, we estimate tensions of at least 10 pN. Occasionally, cell bodies came free and were pulled forward by pilus retraction. Thus, type IV pili are linear actuators that extend, attach at their distal tips, exert substantial force, and retract.

Fimbriae, Bacterial↗

PubMed1993

Structure-function and biogenesis of the type IV pili.

Type IV pili are adhesins expressed by a number of diverse gram-negative microorganisms. These pili are related through similarities in the primary amino acid sequences of the structural subunits, a conserved assembly machinery, and a similar mechanism of transcriptional regulation. Type IV pilus assembly is preceded by proteolytic processing and N-methylation of the pilin polypeptide. This process is carried out by a novel bifunctional enzyme PilD, first identified in Pseudomonas aeruginosa. Moreover, proteins homologous with type IV pilins have been shown to function in extracellular protein secretion in gram-negative bacteria and in transformation competence in gram-positive microorganisms. Like prepilin, these proteins are also processed and N-methylated by PilD. Transcription of the genes for type IV pilins is carried out by an RNA polymerase with a minor sigma factor, RpoN. In P. aeruginosa two other regulatory elements (PilS and PilR) are required for pilin expression. RpoN, but not PilS and PilR, is required for expression of a diverse set of bacterial genes. Therefore, regulation of synthesis and posttranslational modification and assembly of type IV pili serves as a useful model for a number of diverse biological processes in the bacterial cell.

Amino Acid Sequence↗

PubMed2004

Pulling together with type IV pili.

Type IV pili are an efficient and versatile device for bacterial surface motility. They are widespread among the beta-, gamma-, and delta-proteobacteria and the cyanobacteria. Within that diversity, there is a core of conserved proteins that includes the pilin (PilA), the motors PilB and PilT, and various components of pilus biogenesis and assembly, PilC, PilD, PilM, PilN, PilO, PilP, and PilQ. Progress has been made in understanding the motor and the secretory functions. PilT is a motor protein that catalyzes pilus retraction; PilB may play a similar role in pilus extension. Type IV pili are multifunctional complexes that can act as bacterial virulence factors because pilus-based motility is used to spread pathogens over the surface of a tissue, or to build multicellular structures such as biofilms and fruiting bodies.

Bacteria↗

PubMed2006

Gonococci exit apically and basally from polarized epithelial cells and exhibit dynamic changes in type IV pili.

Type IV pili are a major virulence factor of the obligate human pathogen Neisseria gonorrhoeae (the gonococcus; Gc). Pili facilitate bacterial adherence to epithelial cells, but their participation in later steps of epithelial infection, particularly intracellular replication and exit, is poorly understood. Using polarized T84 cells as a model for mature mucosal epithelia, pilus dynamics in piliated, Opa-expressing Gc were examined over time. T84 infection was characterized by a several-hour delay in the growth of cell-associated bacteria and by non-directional exit of Gc, the first time these phenomena have been reported. During infection, non-piliated progeny arose stochastically from piliated progenitors. Piliated and non-piliated Gc replicated and exited from T84 cell monolayers equally well, demonstrating that piliation did not influence Gc survival during epithelial infection. The frequency with which pilin variants arose from a defined piliated progenitor during T84 cell infection was found to be sufficiently high to account for the extensive pilin variation reported during human infection. However, the repertoire of variants appearing in association with T84 cells was similar to what was seen in the absence of cells, demonstrating that polarized epithelial cells can support Gc replication without selecting for a subset of pilin variants or piliation states.

Bacterial Adhesion↗

PubMed2006

Type IV pili and type II secretion play a limited role in Legionella pneumophila biofilm colonization and retention.

Legionellae colonize biofilms in building water systems, yet little is known about their interaction with the organisms in these microbial communities. The role of Legionella pneumophila type IV pili and the type II secretion pre-pilin peptidase was evaluated in a model biofilm system. L. pneumophila strains 130b (wild-type), BS100 (a type IV pili mutant) and NU243 (a pre-pilin peptidase mutant) were assessed for attachment and retention in an established biofilm. Strains 130b and NU243 colonized the biofilm at a similar level while BS100 attached at a tenfold lower level. Over time, NU243 dropped below the level of detection while BS100 remained in the biofilm throughout the course of the experiment. The wild-type strain decreased but remained at a considerably higher level than either of the mutants. Inclusion of amoebae with BS100 allowed for attachment and retention at a level similar to 130b. NU243, which displays reduced intracellular replication, was able to establish itself and persist in the presence of amoebae. Thus, type IV pili and the pre-pilin peptidase facilitate L. pneumophila colonization of biofilms but are not required in the presence of a host for intracellular replication.

Amoebida↗

PubMed2006

A systematic genetic analysis in Neisseria meningitidis defines the Pil proteins required for assembly, functionality, stabilization and export of type IV pili.

Although type IV pili (Tfp) are among the commonest virulence factors in bacteria, their biogenesis by complex machineries of 12-15 proteins, and thereby their function remains poorly understood. Interestingly, some of these proteins were reported to merely antagonize the retraction of the fibres powered by PilT, because piliation could be restored in their absence by a mutation in the pilT gene. The recent identification of the 15 Pil proteins dedicated to Tfp biogenesis in Neisseria meningitidis offered us the unprecedented possibility to define their exact contribution in this process. We therefore systematically introduced a pilT mutation into the corresponding non-piliated mutants and characterized them for the rescue of Tfp and Tfp-mediated virulence phenotypes. We found that in addition to the pilin, the main constituent of Tfp, only six Pil proteins were required for the actual assembly of the fibres, because apparently normal fibres were restored in the remaining mutants. Restored fibres were surface-exposed, except in the pilQ/T mutant in which they were trapped in the periplasm, suggesting that the PilQ secretin was the sole Pil component necessary for their emergence on the surface. Importantly, although in most mutants the restored Tfp were not functional, the pilG/T and pilH/T mutants could form bacterial aggregates and adhere to human cells efficiently, suggesting that Tfp stabilization and functional maturation are two discrete steps. These findings have numerous implications for understanding Tfp biogenesis/function and provide a useful groundwork for the characterization of the precise function of each Pil protein in this process.

Bacterial Proteins↗

PubMed2005

DNA binding: a novel function of Pseudomonas aeruginosa type IV pili.

The opportunistic pathogen Pseudomonas aeruginosa produces multifunctional, polar, filamentous appendages termed type IV pili. Type IV pili are involved in colonization during infection, twitching motility, biofilm formation, bacteriophage infection, and natural transformation. Electrostatic surface analysis of modeled pilus fibers generated from P. aeruginosa strain PAK, K122-4, and KB-7 pilin monomers suggested that a solvent-exposed band of positive charge may be a common feature of all type IV pili. Several functions of type IV pili, including natural transformation and biofilm formation, involve DNA. We investigated the ability of P. aeruginosa type IV pili to bind DNA. Purified PAK, K122-4, and KB-7 pili were observed to bind both bacterial plasmid and salmon sperm DNA in a concentration-dependent and saturable manner. PAK pili had the highest affinity for DNA, followed by K122-4 and KB-7 pili. DNA binding involved backbone interactions and preferential binding to pyrimidine residues even though there was no evidence of sequence-specific binding. Pilus-mediated DNA binding was a function of the intact pilus and thus required elements present in the quaternary structure. However, binding also involved the pilus tip as tip-specific, but not base-specific, antibodies inhibited DNA binding. The conservation of a Thr residue in all type IV pilin monomers examined to date, along with the electrostatic data, implies that DNA binding is a conserved function of type IV pili. Pilus-mediated DNA binding could be important for biofilm formation both in vivo during an infection and ex vivo on abiotic surfaces.

Amino Acid Sequence↗

PubMed1999

Type IV pili and cell motility.

Type IV pili (Tfp) mediate the movement of bacteria over surfaces without the use of flagella. These movements are known as social gliding in Myxococcus xanthus and twitching in organisms such as Pseudomonas aeruginosa and Neisseria gonorrhoeae. Tfp are localized polarly. Type IV pilins have a signature N-terminal domain, which forms a coiled-coil with other monomer units to polymerize a pilus fibre. At least 10 more proteins at the base of the fibre are conserved; they are related to the type II secretion system. Movements produced by Tfp range from short, jerky displacements to lengthy, smooth ones. Tfp also participate in cell-cell interactions, pathogenesis, biofilm formation, natural DNA uptake, auto-aggregation of cells and development. What is the means by which Tfp bring about the movement of cells?

Adenosine Triphosphatases↗

PubMed2005

Surface plasmon resonance shows that type IV pili are important in surface attachment by Pseudomonas aeruginosa.

Type IV pili have been shown to play a role in the early stages of bacterial biofilm formation, but not in initial bacterial attachment. Here, using the surface analytical technique, surface plasmon resonance (SPR), we follow the attachment of the bacterium Pseudomonas aeruginosa in real time. In contrast to previous studies, we show that type IV pili mutants are defective in attachment. Both mutants lacking pili (pilA), and those possessing an overabundance of pili (pilT), showed reduced SPR measured attachment compared with the wild-type PAO1 strain. Both pil mutants also showed reduced pathogenicity in a model insect host, as measured by percentage mortality after 24h. SPR revealed differences in the kinetics of attachment between pilA and pilT, differences obscured by endpoint assays using crystal violet stain. These results highlight the power of SPR in monitoring bacterial attachment in real time and also demonstrate an additional role for type IV pili beyond bacterial aggregation and micro-colony formation.

Fimbriae, Bacterial↗

PubMed1999

Natural competence for DNA transformation by Legionella pneumophila and its association with expression of type IV pili.

We have recently described the expression of two pili of different lengths on the surface of Legionella pneumophila (B. J. Stone and Y. Abu Kwaik, Infect. Immun. 66:1768-1775, 1998). Production of long pili requires a functional pilEL locus, encoding a type IV pilin protein. Since type IV pili in Neisseria gonorrhoeae are associated with competence for DNA transformation, we examined the competence of L. pneumophila for DNA transformation under conditions that allowed the expression of type IV pili. We show that L. pneumophila is naturally competent for DNA transformation by isogenic chromosomal DNA and by plasmid DNA containing L. pneumophila DNA. Many different L. pneumophila loci are able to transform L. pneumophila after addition of plasmid DNA, including gspA, ppa, asd, and pilEL. The transformation frequency is reduced when competing DNA containing either L. pneumophila DNA or vector sequences is added to the bacteria, suggesting that uptake-specific sequences may not be involved in DNA uptake. Competence for DNA transformation correlates with expression of the type IV pili, and a pilEL mutant defective in expression of type IV pili is not competent for DNA transformation. Complementation of the mutant for competence is restored by the reintroduction of a cosmid that restores production of type IV pili. Minimal competence is restored to the mutant by introduction of pilEL alone. We conclude that competence for DNA transformation in L. pneumophila is associated with expression of the type IV pilus and results in recombination of L. pneumophila DNA into the chromosome. Since expression of type IV pili also facilitates attachment of L. pneumophila to mammalian cells and protozoa, we designated the type IV pili CAP (for competence- and adherence-associated pili).

Bacterial Proteins↗

PubMed2000

Effects of bfp mutations on biogenesis of functional enteropathogenic Escherichia coli type IV pili.

Enteropathogenic Escherichia coli expresses a type IV fimbria known as the bundle-forming pilus (BFP) that is required for autoaggregation and localized adherence (LA) to host cells. A cluster of 14 genes is sufficient to reconstitute BFP biogenesis in a laboratory strain of E. coli. We have undertaken a systematic mutagenesis of the individual genes to determine the effect of each mutation on BFP biogenesis and LA. Here we report the construction and analysis of nonpolar mutations in six genes of the bfp cluster, bfpG, bfpB, bfpC, bfpD, bfpP, and bfpH, as well as the further analysis of a previously described bfpA mutant strain that is unable to express bundlin, the pilin protein. We found that mutations in bfpB, which encodes an outer membrane protein; bfpD, which encodes a putative nucleotide-binding protein; and bfpG and bfpC, which do not have sequence homologues in other type IV pilus systems, do not affect prebundlin expression or processing but block both BFP biogenesis and LA. The mutation in bfpP, the prepilin peptidase gene, does not affect prebundlin expression but blocks signal sequence cleavage of prebundlin, BFP biogenesis, and LA. The mutation in bfpH, which is predicted to encode a lytic transglycosylase, has no effect on prebundlin expression, prebundlin processing, BFP biogenesis, or LA. For each mutant for which altered phenotypes were detected, complementation with a plasmid containing the corresponding wild-type allele restored the wild-type phenotypes. We also found that association of prebundlin or bundlin with sucrose density flotation gradient fractions containing both inner and outer membrane proteins does not require any accessory proteins. These studies indicate that many bfp gene products are required for biogenesis of functional type IV pili but that mutations in the individual genes do not lead to the identification of new phases of pilus assembly.

Escherichia coli↗

PubMed2003

Biofilm formation by Pseudomonas aeruginosa wild type, flagella and type IV pili mutants.

Biofilm formation by Gfp-tagged Pseudomonas aeruginosa PAO1 wild type, flagella and type IV pili mutants in flow chambers irrigated with citrate minimal medium was characterized by the use of confocal laser scanning microscopy and comstat image analysis. Flagella and type IV pili were not necessary for P. aeruginosa initial attachment or biofilm formation, but the cell appendages had roles in biofilm development, as wild type, flagella and type IV pili mutants formed biofilms with different structures. Dynamics and selection during biofilm formation were investigated by tagging the wild type and flagella/type IV mutants with Yfp and Cfp and performing time-lapse confocal laser scanning microscopy in mixed colour biofilms. The initial microcolony formation occurred by clonal growth, after which wild-type P. aeruginosa bacteria spread over the substratum by means of twitching motility. The wild-type biofilms were dynamic compositions with extensive motility, competition and selection occurring during development. Bacterial migration prevented the formation of larger microcolonial structures in the wild-type biofilms. The results are discussed in relation to the current model for P. aeruginosa biofilm development.

Biofilms↗

PubMed2004

Expression of type IV pili by Moraxella catarrhalis is essential for natural competence and is affected by iron limitation.

Type IV pili, filamentous surface appendages primarily composed of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of pathogenic bacteria. Although previous electron microscopic studies suggested that pili might be present on the surface of Moraxella catarrhalis isolates, detailed molecular and phenotypic analyses of these structures have not been reported to date. We identified and cloned the M. catarrhalis genes encoding PilA, the major pilin subunit, PilQ, the outer membrane secretin through which the pilus filament is extruded, and PilT, the NTPase that mediates pilin disassembly and retraction. To initiate investigation of the role of this surface organelle in pathogenesis, isogenic pilA, pilT, and pilQ mutants were constructed in M. catarrhalis strain 7169. Comparative analyses of the wild-type 7169 strain and three isogenic pil mutants demonstrated that M. catarrhalis expresses type IV pili that are essential for natural genetic transformation. Our studies suggest type IV pilus production by M. catarrhalis is constitutive and ubiquitous, although pilin expression was demonstrated to be iron responsive and Fur regulated. These data indicate that additional studies aimed at elucidating the prevalence and role of type IV pili in the pathogenesis and host response to M. catarrhalis infections are warranted.

Bacterial Outer Membrane Proteins↗

PubMed2005

Analysis of the pilU gene for the prepilin peptidase involved in the biogenesis of type IV pili encoded by plasmid R64.

In many type IV pili, the N-terminal amino acid of the pilin subunit is N-methylated phenylalanine. A prepilin peptidase removes the leader peptide from the precursor and methylates the amino group of the newly formed phenylalanine. PilS, the precursor of the pilin encoded by plasmid R64, is processed by the prepilin peptidase PilU, but the N-terminal amino acid of the mature pilin is a non-methylated tryptophan that is otherwise modified. To study the relationship between the structure and function of PilU, 42 missense pilU mutations were constructed by PCR and site-directed mutagenesis, and the ability of these pilU mutants to complement a pilU null mutant for mating in liquid culture was analyzed. Although practically no conjugation was noted for 21 of the mutants, the remaining 21 supported varying levels of residual plasmid transfer activity. Two mutants with aspartic acid replacements in conserved motifs exhibited no PilU activity, suggesting that the product of the pilU gene is an aspartic acid peptidase, like TcpJ, the prepilin peptidare of Vibrio cholerae. No PilS processing was detected in 21 of the mutants, but the remaining 21 exhibited varying levels of residual PilS processing. A close correlation was noted between residual PilS processing activity and conjugative transfer, suggesting that the pilU gene product possesses prepilin peptidase activity, but is unable to methylate the N-terminal tryptophan. Based on the activity of pilU-phoA and pilU-lacZ fusion genes encoding different segments of PilU, a model for the membrane topology of the protein is also proposed. Furthermore, some amino acid substitutions in the pilU portion of the pilU-phoA and pilU-lacZ fusion genes were found to alter the membrane topology of the product.

Amino Acid Sequence↗

PubMed2003

A novel ColV plasmid encoding type IV pili.

Many septicaemic Escherichia coli strains harbour ColV virulence plasmids. This paper describes pO78V, a conjugative ColV plasmid from an avian pathogenic E. coli strain that encodes type IV pili in addition to other virulence-related genes and tetracycline resistance. Plasmid location of type IV pili genes was demonstrated using Southern hybridization and expression of the pili was demonstrated using RT-PCR and phage sensitivity assays. This is a first report of a ColV plasmid encoding type IV pili. Plasmid pO78V is a mosaic plasmid containing replicons and other genes typical to both IncI1 and IncFII groups. As type IV pili of Gram-negative bacteria are involved in several stages of infection, their presence on a ColV virulence plasmid could expand the repertoire of pathogenesis-related genes.

Animals↗

PubMed1999

Type IV pili of pathogenic Neisseriae elicit cortical plaque formation in epithelial cells.

The pathogenic Neisseriae Neisseria meningitidis and Neisseria gonorrhoeae, initiate colonization by attaching to host cells using type IV pili. Subsequent adhesive interactions are mediated through the binding of other bacterial adhesins, in particular the Opa family of outer membrane proteins. Here, we have shown that pilus-mediated adhesion to host cells by either meningococci or gonococci triggers the rapid, localized formation of dramatic cortical plaques in host epithelial cells. Cortical plaques are enriched in both components of the cortical cytoskeleton and a subset of integral membrane proteins. These include: CD44v3, a heparan sulphate proteoglycan that may serve as an Opa receptor; EGFR, a receptor tyrosine kinase; CD44 and ICAM-1, adhesion molecules known to mediate inflammatory responses; f-actin; and ezrin, a component that tethers membrane components to the actin cytoskeleton. Genetic analyses reveal that cortical plaque formation is highly adhesin specific. Both pilE and pilC null mutants fail to induce cortical plaques, indicating that neisserial type IV pili are required for cortical plaque induction. Mutations in pilT, a gene required for pilus-mediated twitching motility, confer a partial defect in cortical plaque formation. In contrast to type IV pili, many other neisserial surface structures are not involved in cortical plaque induction, including Opa, Opc, glycolipid GgO4-binding adhesins, polysialic acid capsule or a particular lipooligosaccharide variant. Furthermore, it is shown that type IV pili allow gonococci to overcome the inhibitory effect of heparin, a soluble receptor analogue, on gonococcal invasion of Chang and A431 epithelial cells. These and other observations strongly suggest that type IV pili play an active role in initiating neisserial infection of the mucosal surface in vivo. The functions of type IV pili and other neisserial adhesins are discussed in the specific context of the mucosal microenvironment, and a multistep model for neisserial colonization of mucosal epithelia is proposed.

Animals↗

PubMed1999

Functional characterization of type IV pili expressed on diarrhea-associated isolates of Aeromonas species.

Our past work has shown that long, flexible type IV pili (single or in bundles) are the predominant pili expressed on fecal isolates of diarrhea-associated species of Aeromonas (Aeromonas veronii biovar sobria and A. caviae). They represent a family of type IV pili which we have designated Bfp (for bundle-forming pili). Reports from Japan suggest that Bfp are intestinal colonization factors. This study presents compelling evidence to support this conclusion. Aeromonas bacteria and/or Bfp purified from a strain of A. veronii biovar sobria were shown to adhere to epithelial and intestinal cell lines, freshly isolated human enterocytes, and fresh and fixed human and rabbit intestinal tissues, as determined by light and electron microscopy and immunohistochemical detection. Removal of Bfp by mechanical means decreased adhesion to cell lines by up to 80%. Purified Bfp blocked adhesion of the test strain to intestinal cells in a dose-dependent manner. Adhesion was also blocked by the Fab fraction of anti-Bfp immunoglobulin G. Moreover, ultrastructural studies (ruthenium red staining and transmission and scanning electron microscopy) demonstrated for the first time that Aeromonas adhesion to human enterocytes is pilus mediated and suggested that Bfp may also promote colonization by forming bacterium-to-bacterium linkages. Bfp-positive isolates examined for type IV pilus-mediated twitching motility in agar and slide culture assays developed for Pseudomonas aeruginosa did not, however, exhibit this function.

Aeromonas↗

PubMed2006

Two type IV pili of Vibrio parahaemolyticus play different roles in biofilm formation.

Vibrio parahaemolyticus RIMD2210633 has two sets of type IV-A pilus genes. One set is similar to that found in other Gram-negative bacteria, such as Pseudomonas aeruginosa, Vibrio cholerae (chitin-regulated pilus; ChiRP), and Vibrio vulnificus. The other is homologous to the genes for the mannose-sensitive hemagglutinin (MSHA) pilus. In this study, we analyzed the effects of the deletions in the pilin genes for each type IV pilus (the ChiRP and the MSHA pilus) on biofilm formation. Although the MSHA pilin mutant formed aggregates, the number of bacteria that attached directly to the coverslip was reduced, suggesting that this pilus contributes to the bacterial attachment to the surface of the coverslip. In contrast, the ChiRP mutant attached to the surface of the coverslip, but did not form aggregates, suggesting that ChiRP plays a role in bacterial agglutination during biofilm formation. These results suggest that the two type IV pili of V. parahaemolyticus contribute to biofilm formation in different ways. Both mutants showed a lower fitness for adsorption onto chitin particles than that of the wild type. Collectively, these data suggest that the use of two type IV pili is a refined strategy of V. parahaemolyticus for survival in natural environments.

Bacterial Adhesion↗