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PubMed2003

A common dominant TLR5 stop codon polymorphism abolishes flagellin signaling and is associated with susceptibility to legionnaires' disease.

Although Toll-like receptors (TLRs) are critical mediators of the immune response to pathogens, the influence of polymorphisms in this gene family on human susceptibility to infection is poorly understood. We demonstrated recently that TLR5 recognizes flagellin, a potent inflammatory stimulus present in the flagellar structure of many bacteria. Here, we show that a common stop codon polymorphism in the ligand-binding domain of TLR5 (TLR5392STOP) is unable to mediate flagellin signaling, acts in a dominant fashion, and is associated with susceptibility to pneumonia caused by Legionella pneumophila, a flagellated bacterium. We also show that flagellin is a principal stimulant of proinflammatory cytokine production in lung epithelial cells. Together, these observations suggest that TLR5392STOP increases human susceptibility to infection through an unusual dominant mechanism that compromises TLR5's essential role as a regulator of the lung epithelial innate immune response.

Codon, Terminator↗

PubMed1984

Genetic mapping of genes required for motility in Caulobacter crescentus.

Mutations in more than 30 genes affect motility in Caulobacter crescentus. We have determined the chromosomal map locations for 27 genes involved in flagellar morphogenesis (fla), three genes involved in flagellar function (mot), and three genes that have a pleiotropic effect on both motility and bacteriophage resistance (ple). Three multigene clusters have been detected at widely separated chromosomal locations, but in addition, there are 12 fla and mot genes that are found at eight additional sites scattered around the C. crescentus chromosome. Thus, there is more scatter of genes involved in flagellar structure and function than has been observed in other bacterial systems.

Bacteria↗

PubMed1983

The role of the flagellum in the adherence of Vibrio cholerae.

The role of the flagellar structure in the in vitro adherence and in vivo colonization of Vibrio cholerae was studied by comparing the behavior of pairs of related motility variants. Although the presence of the flagellum seemed essential for in vitro attachment, the property of motility was neither necessary nor sufficient. Since it was possible to demonstrate independently both motility and binding capacities associated with this structure, it was concluded that the flagellum functions as the carrier of the moieties that promote adherence. Studies using the infant mouse cholera model unequivocally demonstrated the in vivo significance of a functional flagellum and suggested that this structure enhances virulence by facilitating the initial colonization of the small bowel.

Adhesiveness↗

PubMed1996

Flagellin gene and protein variation amongst clinical isolates of Pseudomonas aeruginosa.

Flagellin gene sequences from 64 clinical isolates of the opportunistic pathogen Pseudomonas aeruginosa were amplified by PCR and subjected to RFLP analysis by using seven restriction enzymes to digest the amplified products. Using this approach the isolates were assigned to one of 13 groups. The method was rapid, reproducible and applicable to all isolates. In contrast, serotyping failed to satisfactorily resolve 49% of the strains tested. The vast majority of clinical isolates generated amplified products of 1.02 kb (type a) or 1.25 kb (type b). Electron microscopical analysis revealed evidence fax some. flagellar structural variation between P. aeruginosa strains. This study provides further evidence that the flagellin gene is a widely applicable and useful genetic marker for studying genetic variation within populations of closely related bacteria.

Base Sequence↗

PubMed2003

Effects of quorum sensing on flaA transcription and autoagglutination in Campylobacter jejuni.

Some bacteria can communicate with other species of bacteria by means of autoinducer-2 (AI-2)-mediated quorum sensing. In this study, we demonstrated that AI-2-mediated quorum sensing influences the transcription of flaA, the major flagellin gene in Campylobacter jejuni. A null mutation of luxS in C. jejuni strain 81116 reduced flaA transcription (approximately 43% that of the wild-type) and induced a reduction in motility. However, the luxS mutant had the same level of total flagellin protein as the wild-type. Transmission electron microscopy showed that the flagellar structure was preserved in the luxS mutant. The agglutination capability was reduced in the mutant strain, implying that quorum sensing might be involved in the formation of surface structures of C. jejuni. These observations suggest that AI-2-mediated quorum sensing may play a role in regulation of motility and surface properties in C. jejuni.

Agglutination↗

PubMedDate not supplied

Outer dense fibres: functional or structural elements?

By electron microscopic studies it could be demonstrated that malformed outer dense fibres are a major cause of structural, flagellar disorder in human spermatozoa. Biochemical investigations of isolated outer dense fibres revealed that these flagellar substructures consist of three major polypeptides and do not contain phosphoproteins. They seem to have passive-elastic properties with respect to sperm motility. Further studies are required to elucidate the cause of the disturbed development of outer dense fibres, which may be due to inflammatory, toxic, or genetic influences.

Electrophoresis, Polyacrylamide Gel↗

PubMedDate not supplied

Reconstruction of the flagellar apparatus in Ploeotia costata (Euglenozoa) and its relationship to other euglenoid flagellar apparatuses.

The flagellar apparatus of Ploeotia costata Farmer and Triemer was reconstructed using serial sectioning and TEM. The flagellar apparatus is similar to other euglenoids having two flagella arising from basal bodies connected by a striated fiber, and three asymmetrically arranged roots. The flagella emerge subapically from between the two ventral pellicle strips. The dorsal flagellum is 1/2 the body length and actively pulls the cell, while the ventral flagellum is twice the body length and drags along the substrate surface. The ventral and dorsal roots are on the opposite sides of their respective basal bodies, while the intermediate root is associated with the ventral flagellum on the side closest to the dorsal basal body. The dorsal root lines the dorsal side of the reservoir and after giving rise to the dorsal band lines the right side of the reservoir/canal. The ventral and intermediate roots join at the reservoir forming the intermediate-ventral root, which lines the left and ventral sides of the reservoir/canal. There was no evidence of a microtubule-reinforced pocket in P. costata. Comparisons with Ploeotia vilrea, Lentomonas applanatum, and related flagellar apparatuses led to the conclusion that the basic euglenoid flagellar structure is symplesiomorphic but with enough variation to be taxonomically diagnostic.

Animals↗

PubMed1999

Molecular characterization of a flagellar (fla) operon in the oral spirochete Treponema denticola ATCC 35405.

A Treponema denticola 9.6-kb motility locus containing 11 genes was identified, sequenced and analyzed. The genes were designated tap1, flgD, flgE, orf4, motA, motB, fliL, fliM, fliY, orf10 and fliP. The order of these genes is identical to that of the corresponding region of the Treponema pallidum fla operon. Seven of the deduced Fla proteins share significant homology with both Escherichia coli and Bacillus subtilis proteins associated with flagellar structure and function. Reverse transcription-PCR analysis indicated that the T. denticola fla genes are transcribed as a single unit. A putative sigma(28)-like promoter, virtually identical to the T. pallidum fla promoter, was identified upstream of tap1. These results showed that the T. denticola and T. pallidum fla operons are highly conserved, supporting the proposed phylogenetic relatedness of these spirochetes.

Bacterial Proteins↗

PubMed2001

Transposon mutations in the flagella biosynthetic pathway of the solvent-tolerant Pseudomonas putida S12 result in a decreased expression of solvent efflux genes.

Fourteen solvent-sensitive transposon mutants were generated from the solvent-tolerant Pseudomonas putida strain S12 by applying the TnMod-KmO mutagenesis system. These mutants were unable to grow in the presence of octanol and toluene. By cloning the region flanking the transposon insertion point a partial sequence of the interrupted genes was determined. Comparison of the deduced amino acid sequences with a protein database revealed the following interrupted putative gene products: organic solvent efflux proteins SrpA and SrpB, the flagellar structural proteins FlgK, FlaG, FliI, FliC, and FliH, the transcriptional activator FleQ, the alternative RNA polymerase sigma factor RpoN, and the flagellum-specific RNA polymerase sigma factor FliA (RpoF). The transposon mutants, except for the organic solvent efflux mutants, were nonmotile as determined by a swarm assay and the formation of the flagellum was totally impaired. Expression studies with a srp promoter probe showed a decreased expression of the SrpABC efflux pump in the nonmotile mutants.

Bacterial Proteins↗

PubMed1995

Swarming and Swimming Changes Concomitant with Phase Variation in Xenorhabdus nematophilus.

Xenorhabdus spp., entomopathogenic bacteria symbiotically associated with nematodes of the family Steinernematidae, occur spontaneously in two phases. Phase I, the variant naturally isolated from the infective-stage nematode, provides better conditions than the phase II variant for nematode reproduction. This study has shown that Xenorhabdus phase I variants displayed a swarming motility when they were grown on a suitable solid medium (0.6 to 1.2% agar). Whereas most of the phase I variants from different Xenorhabdus spp. were able to undergo cycle of rapid and coordinately population migration over the surface, phase II variants were unable to swarm and even to swim in semisolid agar, particularly in X. nematophilus. Optical and electron microscopic observations showed nonmotile cells with phase II variants of X. nematophilus F1 which lost their flagella. Flagellar filaments from strain F1 phase I variants were purified, and the molecular mass of the flagellar structural subunit was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 36.5 kDa. Flagellin from cellular extracts or culture medium of phase II was undetectable with antiserum against the denatured flagellin by immunoblotting analysis. This suggests that the lack of flagella in phase II cells is due to a defect during flagellin synthesis. The importance of such a difference of motility between both phases is discussed in regard to adaptation of these bacteria to the insect prey and the nematode host.

Journal Article↗

PubMed2003

A negative regulatory element controls mRNA abundance of the Leishmania mexicana Paraflagellar rod gene PFR2.

The Leishmania mexicana PFR2 locus encodes a component of the paraflagellar rod (PFR), a flagellar structure found only in the insect stage of the life cycle. PFR2 mRNA levels are 10-fold lower in the mammalian stage than in the insect stage. Nuclear run-on experiments indicate that the change in PFR2 mRNA abundance is achieved posttranscriptionally. Deletion and block substitution analysis of the entire 1,400-nucleotide 3' untranslated region (UTR) of PFR2C led to the identification of a regulatory element contained within 10 nucleotides of the 3' UTR, termed the PFR regulatory element (PRE), that is necessary for the 10-fold regulation of PFR2 mRNA levels. Comparison of the half-lives of PFR2 transcripts, identical except for the presence or absence of the PRE, revealed that the PRE acts by destabilizing the PFR2 mRNA in amastigotes. The PRE was inserted into a construct which directs the constitutive expression of a chimeric PFR2 transcript. Insertion of the PRE resulted in regulated expression of this transcript, demonstrating that the regulatory element is sufficient for promastigote-specific expression. Since the PRE is present in the 3' UTR of all L. mexicana PFR genes examined so far, we propose that it serves a means of coordinating expression of PFR genes.

3' Untranslated Regions↗

PubMed2006

Listeria monocytogenes flagella are used for motility, not as adhesins, to increase host cell invasion.

Flagellar structures contribute to the virulence of multiple gastrointestinal pathogens either as the effectors of motility, as adhesins, or as a secretion apparatus for virulence factors. Listeria monocytogenes is a food-borne, gram-positive pathogen that uses flagella to increase the efficiency of epithelial cell invasion (A. Bigot, H. Pagniez, E. Botton, C. Frehel, I. Dubail, C. Jacquet, A. Charbit, and C. Raynaud, Infect. Immun. 73:5530-5539, 2005; L. Dons, E. Eriksson, Y. Jin, M. E. Rottenberg, K. Kristensson, C. N. Larsen, J. Bresciani, and J. E. Olsen, Infect. Immun. 72:3237-3244, 2004). In this study, we aimed to elucidate the mechanism by which flagella contribute to L. monocytogenes invasion. To examine the role of flagella as adhesins, invasion and adhesion assays were performed with flagellated motile and nonmotile bacteria and nonflagellated bacteria. We observed that flagellated but nonmotile bacteria do not adhere to or invade human epithelial cells more efficiently than nonflagellated bacteria. These results indicated that flagella do not function as adhesins to enhance the adhesion of L. monocytogenes to targeted host cells. Instead, it appears that motility is important for tissue culture invasion. Furthermore, we tested whether motility contributes to early colonization of the gastrointestinal tract using a competitive index assay in which mice were infected orally with motile and nonmotile bacteria in a 1:1 ratio. Differential bacterial counts demonstrated that motile bacteria outcompete nonmotile bacteria in the colonization of the intestines at early time points postinfection. This difference is also reflected in invasion of the liver 12 h later, suggesting that flagellum-mediated motility enhances L. monocytogenes infectivity soon after bacterial ingestion in vivo.

Adhesins, Bacterial↗

PubMed1991

Proteus mirabilis flagella and MR/P fimbriae: isolation, purification, N-terminal analysis, and serum antibody response following experimental urinary tract infection.

Urinary tract infection with Proteus mirabilis may lead to serious complications, including cystitis, acute pyelonephritis, fever, bacteremia, and death. In addition to the production of hemolysin and the enzyme urease, fimbriae and flagellum-mediated motility have been postulated as virulence factors for this species. We purified mannose-resistant/proteuslike (MR/P) fimbriae and flagella from strains CFT322 and HU2450, respectively. Electron microscopy revealed highly concentrated preparations of fimbriae and flagella. Fimbrial and flagellar structural subunits were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 18.5 and 41 kDa, respectively. N-terminal sequencing revealed that 10 of the first 20 amino acids of the major MR/P subunit matched the sequence of the P. mirabilis uroepithelial cell adhesin N terminus and 11 of 20 amino acids matched the predicted amino acid sequence of the Escherichia coli P fimbriae structural subunit, PapA. In addition, 90 and 80% homologies were found between the first 20 amino acids of P. mirabilis flagellin and those of Salmonella typhimurium phase-1 flagellin and the E. coli hag gene product, respectively. An enzyme-linked immunosorbent assay using purified antigens showed a strong reaction between the MR/P fimbriae or flagella and sera of CBA mice challenged transurethrally with P. mirabilis. A possible role for MR/P fimbriae in the pathogenesis of urinary tract infection is supported by (i) a strong immune response to the antigen in experimentally infected animals, (ii) amino acid sequence similarity to other enteric surface structure, and (iii) our previously reported observation that MR/P fimbriae are expressed preferentially as the sole fimbrial type in human pyelonephritis isolates.

Amino Acid Sequence↗

PubMed1998

Salmonella flagellin induces tumor necrosis factor alpha in a human promonocytic cell line.

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 the human promonocytic cell line U38. In this model system, cytokine upregulation is not due to lipopolysaccharide but is mediated by a released protein. In the present study, TnphoA transposon mutagenesis was used to identify the TNF-alpha-inducing factor. A mutant Salmonella strain which lacks the ability to induce TNF-alpha was isolated from a TnphoA library. Genetic analysis of this mutant demonstrated that the hns gene has been interrupted by transposon insertion. The hns gene product is a DNA-binding protein that regulates the expression of a variety of unrelated genes in salmonellae. One of the known targets of histone-like protein H1 is flhDC, the master operon which is absolutely required for flagellar expression. Analysis of other nonflagellated mutant Salmonella strains revealed a correlation between the ability to induce TNF-alpha and the expression of the phase 1 filament subunit protein FliC. Complementation experiments demonstrated that FliC is sufficient to restore the ability of nonflagellated mutant Salmonella strains to upregulate TNF-alpha, whereas the phase 2 protein FljB appears to complement to a lesser extent. In addition, Salmonella FliC can confer the TNF-alpha-inducing phenotype on Escherichia coli, which otherwise lacks the activity. Furthermore, assembly of FliC into complete flagellar structures may not be required for induction of TNF-alpha.

Cell Line↗

PubMed2004

Involvement of lipoprotein NlpI in the virulence of adherent invasive Escherichia coli strain LF82 isolated from a patient with Crohn's disease.

Escherichia coli strain LF82 recovered from a chronic lesion of a patient with Crohn's disease (CD) is able to adhere to and invade cultured intestinal epithelial cells and to replicate within macrophages. One mutant selected for its impaired ability to invade epithelial cells had an insertion of a Tn phoA transposon within the nlpI gene encoding the lipoprotein NlpI. A NlpI-negative isogenic mutant showed a 35-fold decrease in its ability to adhere to and a 45-fold decrease in its ability to invade Intestine-407 cells, but its ability to survive and to replicate within macrophages was similar to that of wild-type strain LF82. In addition, this mutant did not express flagella and synthesized very small amounts of type 1 pili. Downregulation of type 1 pili in the NlpI-negative mutant resulted from a preferential switch toward the OFF position of the invertible DNA element located upstream of the fim operon. The FimB and FimE recombinases act in concert to control the switch, and a large decrease in fimB and fimE mRNA levels was observed. The absence of flagellar structures correlated with a drastic 19-fold decrease in the fliC mRNA level, regardless of the FlhD(2)C(2) transcriptional regulator and of the sigma(28) transcription factor. The key role of NlpI in virulence is independent of type 1 pili and motility, since induced type 1 pilus expression and/or forced contact between bacteria and intestinal epithelial cells did not restore the ability of the NlpI mutant to adhere to and to invade intestinal epithelial cells.

Bacterial Adhesion↗

PubMed2005

HosA, a member of the SlyA family, regulates motility in enteropathogenic Escherichia coli.

In enteropathogenic and enterohemorraghic Escherichia coli (EPEC and EHEC), two members of the SlyA family of transcriptional regulators have been identified as SlyA. Western blot analysis of the wild type and the corresponding hosA and slyA deletion mutants indicated that SlyA and HosA are distinct proteins whose expression is not interdependent. Of 27 different E. coli strains (EPEC, EHEC, enteroinvasive, enteroaggregative, uropathogenic, and commensal) examined, 14 were positive for both genes and proteins. To investigate hosA expression, a hosA::luxCDABE reporter gene fusion was constructed. hosA expression was significantly reduced in the hosA but not the slyA mutant and was influenced by temperature, salt, and pH. In contrast to SlyA, HosA did not activate the cryptic E. coli K-12 hemolysin ClyA. Mutation of hosA did not influence type III secretion, the regulation of the LEE1 and LEE4 operons, or the ability of E2348/69 to form attaching-and-effacing lesions on intestinal epithelial cells. HosA is, however, involved in the temperature-dependent positive control of motility on swim plates and regulates fliC expression and FliC protein levels. In electrophoretic mobility shift assays, purified HosA protein bound specifically to the fliC promoter, indicating that HosA directly modulates flagellin expression. While direct examination of flagellar structure and the motile behavior of individual hosA cells grown in broth culture at 30 degrees C did not reveal any obvious differences, hosA mutants, unlike the wild type, clumped together, forming nonmotile aggregates which could account for the markedly reduced motility of the hosA mutant on swim plates at 30 degrees C. We conclude that SlyA and HosA are independent transcriptional regulators that respond to different physicochemical cues to facilitate the environmental adaptation of E. coli.

Amino Acid Sequence↗

PubMed1972

Effect of proteolytic enzymes on bacterial flagella.

Sheared flagella of Salmonella typhimurium strains SL 870 (Nml(+)Fla(+)) and SL 871 (Nml(-)Fla(+)) were found to be susceptible to proteolytic digestion by trypsin, chymotrypsin, and Pronase. The rate of tryptic digestion was similar for the epsilon-N-methyllysine-containing and the nonmethylated flagella. Thin fibers, which appeared to originate from only one end of the flagellar filament, were formed upon trypsin digestion. The fibers were not dissociated at extremes of pH or upon heating. The amino acid composition of the purified fibers was very different from that of intact Salmonella flagellin, and the fibers did not cross-react with antiflagellin or antiflagellar antiserum. The possible significance of these findings is discussed in relation to the flagellar structure.

Amino Acids↗

PubMed1976

Physical characterization of Caulobacter crescentus flagella.

Preparations of intact flagella isolated from Caulobacter crescentus CB13B1a were found to contain two protein species of apparent molecular weights 28,000 and 25,000. Both proteins cross-reacted completely with each other and with purified flagella in Ouchterlony double-immunodiffusion assays. The amino acid compositions of the isolated proteins were similar to one another but precluded any precursor-product relationship. Absence of both the 25,000- and 28,000-molecular-weight proteins from a number of nonmotile mutants and the simultaneous reappearance of these proteins in a motile revertant provide further evidence of the relationship of these two proteins to flagellar structure.

Amino Acids↗