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Lateral flagella are required for increased cell adherence, invasion and biofilm formation by Aeromonas spp.

Two types of flagella are responsible for motility in mesophilic Aeromonas strains. A polar unsheathed flagellum is expressed constitutively that allows the bacterium to swim in liquid environments and, in media where the polar flagellum is unable to propel the cell, Aeromonas express peritrichous lateral flagella. Recently, Southern blot analysis using a DNA probe based on the Aeromonas caviae Sch3N lateral flagellin gene sequence showed a good correlation between strains positive for the DNA probe, swarming motility and the presence of lateral flagella by microscopy. Here, we conclude that the easiest method for the detection of the lateral flagellin gene(s) is by PCR (polymerase chain reaction); this showed good correlation with swarming motility and the presence of lateral flagella. This was despite the high degree of DNA heterogeneity found in Aeromonas gene sequences. Furthermore, by reintroducing the laf (lateral flagella) genes into several mesophilic lateral-flagella-negative Aeromonas wild-type strains, we demonstrate that this surface structure enhances the adhesion to and invasion of HEp-2 cells and the capacity for biofilm formation in vitro. These results, together with previous data obtained using Laf- mutants, demonstrate that lateral flagella production is a pathogenic feature due to its enhancement of the interaction with eukaryotic cell surfaces.

Aeromonas↗

The flagella of enteropathogenic Escherichia coli mediate adherence to epithelial cells.

Enteropathogenic Escherichia coli (EPEC) utilizes a type III protein secretion system to target effector molecules into the host cell leading to effacement of the intestinal mucosa. This secretion apparatus shares many structural features of the flagellar type III export system involved in flagella assembly and motility. We report here that fliC insertional mutants constructed in two wild-type EPEC strains were markedly impaired in adherence and microcolony formation on cultured cells. An E. coli K-12 strain harbouring the EPEC H6 fliC gene on a plasmid showed discrete adhering clusters on HeLa cells, albeit to less extent than the wild-type EPEC strain. Flagella purified from EPEC bound to cultured epithelial cells and antiflagella antibodies blocked adherence of several EPEC serotypes. We determined that eukaryotic cells in culture stimulate expression of flagella by motile and non-motile EPEC. Isogenic strains mutated in perA (a transcriptional activator), bfpA (a type IV pilin), luxS (a quorum-sensing autoinducer gene) and in the type III secretion genes were reduced for motility in Dulbecco's modified Eagle medium (DMEM) motility agar and produced none or few flagella when associated with epithelial cells. Growth of these mutants in preconditioned tissue culture medium restored motility and their ability to produce flagella, suggesting the influence of a signal provided by mammalian cells that triggers flagella production. This study shows for the first time that the flagella of EPEC are directly involved in the adherence of these bacteria and supports the existence of a molecular relationship between the two existing type III secretion pathways of EPEC, the EPEC adherence factor (EAF) plasmid-encoded regulator, quorum sensing and epithelial cells.

Bacterial Adhesion↗

Differences between surface antigenic determinants of polar monotrichous flagella of Vibrio parahaemolyticus and of related species.

Polar monotrichous flagella (M-flagella) of Vibrio parahaemolyticus have antigens in common with those of various species of Vibrio including V. cholerae and V. anguillarum, and of Beneckea, revealed by gel diffusion tests with flagelli monomers. However, antiserum against M-flagellin of V. parahaemolyticus did not agglutinate cells of V. cholerae and V. anguillarum, although it did agglutinate cells of V. parahaemolyticus. Agglutination tests after absorption of the antiserum with purified M-flagellar filaments or flagellin monomers and H-agglutination inhibition tests demonstrated that there are two different antigenic determinants in M-flagella as in lateral flagella. One is on the surface of the M-flagella (surface antigenic determinant, SA) and disappears or is buried in dissociated monomers. The other is inside the flagella (internal antigenic determinant, IA) and is exposed when the flagella are dissociated to flagellin monomers. SA of V. parahaemolyticus is different from those of V. cholerae and V. anguillarum, whereas the three species have a common IA.

Agglutination Tests↗

Studies on the attachment of Leishmania flagella to sand fly midgut epithelium.

An in vitro assay was developed to study the recognition mechanism for attachment of Leishmania flagella to sand fly midgut epithelium. Frozen sections of sand fly guts were incubated with flagella preparations, and probed with a flagella-specific monoclonal antibody. Tissue-specific adhesion of flagella to midgut epithelium was demonstrated by indirect immunofluorescence. None of the 13 sugars, screened to test for possible lectin-mediation, appeared to significantly inhibit the adhesion of flagella to gut sections. Similarly no inhibition was achieved by incubating flagella with pep 63 which inhibits the promastigote-macrophage recognition mechanism. Significant inhibition was attained by incubating flagella preparations with a monoclonal antibody which binds to a flagellar membrane-component. The possible relevance of the described mechanism for the biology of Leishmania in their sand fly hosts, is discussed.

Animals↗

Plain and complex flagella of Pseudomonas rhodos: analysis of fine structure and composition.

Cells of Pseudomonas rhodos 9-6 produce two morphologically distinct flagella termed plain and complex, respectively. Fine structure analyses by electron microscopy and optical diffraction showed that plain flagellar filaments are cylinders of 13-nm diameter composed of globular subunits like normal bacterial flagella. The structure comprises nine large-scale helical rows of subunits intersecting four small-scale helices of pitch angle 25 degrees . Complex filaments have a conspicuous helical sheath, 18-nm wide, of three close-fitting helical bands, each about 4.7-nm wide, separated by axial intervals, 4.7 nm wide, running at an angle of 27 degrees . The internal core has similar but not identical substructure to plain filaments. Unlike plain flagella, the complex species is fragile and does not aggregate in bundles. Mutants bearing only one of two types of flagellum were isolated. Cells with plain flagella showed normal translational motion, and cells with complex flagella showed rapid spinning. Isolated plain flagella consist of a 37,000-dalton subunit separable into two isoproteins. Complex filaments consist of a 55,000-dalton protein; a second 43,000-dalton protein was assigned to complex flagellar hooks. The results indicate that plain and complex flagella are entirely different in structure and composition and that the complex type represents a novel flagellar species. Its possible mode of action is discussed.

Bacterial Proteins↗

Isolation of flagella from the archaebacterium Methanococcus voltae by phase separation with Triton X-114.

The flagella of Methanococcus voltae were isolated by using three procedures. Initially, cells were sheared to release the filaments, which were purified by differential centrifugation and banding in KBr gradients. Flagella were also prepared by solubilization of cells with 1% (vol/vol) Triton X-100 and purified as described above. Both of these techniques resulted in variable recovery and poor yield of flagellar filaments. Purification of intact flagella (filament, hook, and basal body) was achieved by using phase transition separation with Triton X-114. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified flagella revealed two major proteins, with molecular weights of 33,000 and 31,000. This result indicates the likely presence of two flagellins. The filament had a diameter of 13 nm. The basal structure consisted of a small knob, while a slight thickening of the filament immediately adjacent to this area was the only evidence of a hook region. Flagella from three other Methanococcus species were isolated by this technique and found to have the same ultrastructure as flagella from M. voltae. Isolation of flagella from three eubacteria and another methanogen (Methanospirillum hungatei [M. hungatii]) by the phase separation technique indicated that the detergent treatment did not affect the structure of basal bodies. Intact ring structures and well-differentiated hook regions were apparent in each of these flagellar preparations.

Archaea↗

Formation of bacterial flagella. I. Demonstration of a functional flagellin pool in spirillum serpens and bacillus subtilis.

Martinez, R. J. (University of California, Los Angeles), and E. Z. Gordee. Formation of bacterial flagella. I. Demonstration of a functional flagellin pool in Spirillum serpens and Bacillus subtilis. J. Bacteriol. 91:870-875. 1966-Exponentially growing cultures of Spirillum serpens and Bacillus subtilis regained motility and flagella within one generation after mechanical deflagellation. Regeneration of flagella occurred in both cultures in the presence of chloramphenicol at concentrations shown to inhibit flagellin synthesis. Cells labeled with C(14)-amino acids regenerated radioactive flagella in the presence of chloramphenicol. A conditional mutant of S. serpens (T-45) was isolated. This strain did not produce flagella when grown at 45 C, but formed the organelles upon temperature shift to 30 C, even in the presence of chloramphenicol. A reduction of intracellular antibody-precipitable flagellin counts in labeled S. serpens T-45 occurred concomitant with the generation of flagella at 30 C. The data suggest that the flagella of S. serpens and B. subtilis are formed from a pool of intracellular flagellin proteins.

Amino Acids↗

Hypervariable region IV of Salmonella gene fliCd encodes a dominant surface epitope and a stabilizing factor for functional flagella.

To identify the major antigenic determinant of native Salmonella flagella of antigenic type d, we constructed a series of mutated fliCd genes with deletions and amino acid alterations in hypervariable region IV and in region of putative epitopes as suggested by epitope mapping with synthetic octameric peptides (T.M. Joys and F. Schödel, Infect. Immun. 59:3330-3332, 1991). The expressed product of most of the mutant genes, with deletions of up to 92 amino acids in region IV, assembled into functional flagella and conferred motility on flagellin-deficient hosts. Serological analysis of these flagella with different anti-d antibodies revealed that the peptide sequence centered at amino acids 229 to 230 of flagellin was a dominant B-cell epitope at the surface of d flagella, because replacement of these two amino acids alone or together with their flanking sequence by a tripeptide specified by a linker sequence eliminated most reactivity with antisera against wild-type d flagella as tested by enzyme-linked immunosorbent assay or by Western immunoblot. Functional analysis of the mutated flagellin genes with or without an insert suggested that amino acids 180 to 214 in the 5' part of hypervariable region IV (residues 181 to 307 of the total of 505) is important to the function of flagella. The hybrid proteins formed by insertion of peptide sequence pre-S1 12-47 of hepatitis B virus surface antigen into the deleted flagellins assembled into functional flagella, and antibody to the pre-S1 sequence was detected after immunization of mice with the hybrid protein. This suggests that such mutant flagellins containing heterologous epitopes have potential as vaccines.

Amino Acid Sequence↗

"Cap" on the tip of Salmonella flagella.

Flagellar filaments isolated intact from a Salmonella short-flagella mutant are unable to serve as nuclei for flagellin polymerization in vitro, whereas the filaments reconstructed in vitro from the mutant flagellin are able to do so. The inability of intact flagella to nucleate flagellin polymerization appears to be common to wild-type bacteria and thus suggests that the tip of intact flagella are generally inactivated or capped in vivo. Careful observations of the tips of intact flagella and reconstructed flagellar filaments of a wild-type species have revealed marked difference between them: the intact flagella usually have blunt ends, whereas reconstructed filaments have concave, "fish-tail" ends. Moreover, a thin structure is often observed attaching to the very end of the intact flagella. We suspect that this "capping" structure is essential to the elongation mechanism of flagellar filaments.

Flagella↗

Undulipodia, flagella and cilia.

The term flagella is ambiguous. It refers to bacterial structures composed of flagellin protein and to eukaryotic structures composed of microtubule proteins and ATPase (tubulin and dynein). The fact that cilia are nearly identical to eukaryotic flagella and have nothing in common with prokaryotic flagella is not apparent from the terminology. It is proposed that the 30-year old suggestion of Smagina and reiterated by Kuznicki and others, be adopted: that cilia and eukaryotic flagella be called "undulipodia." The term flagella ought to be restricted to prokaryotic organelles, bacterial flagella and spirochaete axial filaments: solid structures composed of flagellin which protrude through the plasma membrane and lack intrinsic motility throughout their length. Undulipodia are defined as intrinsically motile intracellular structures showing a 9-fold symmetry in the pattern of arrangement of 24 nm diameter microtubules. They are limited to eukaryotes, members of the protoctist, animal and plant kingdoms.

Animals↗

Peptide display on bacterial flagella: principles and applications.

Expression of foreign peptides as fusions to bacterial cell surface proteins has gained increasing attention in basic, as well as applied research during the last decade. A wide range of heterologous peptides have been expressed, and the spectrum of available carrier proteins is also wide. The choice of carrier protein is frequently ruled by the application of the fusion protein constructed. This review is focused on flagella display, which is based on genetic fusion of foreign peptides into a surface-exposed, dispensable region of flagellin, the flagellar major subunit present in thousands of copies per filament. Expression of these constructs in flagellin-deficient host strains results in hybrid flagella carrying the heterologous peptides in thousands of intimately-associated copies. The first and still most frequent application of flagella display is the construction of novel recombinant vaccines. Flagella display has also been used in peptide display as an alternative to the phage-display technique. One application involves fusion into a disulfide loop of Escherichia coli thioredoxin that has been inserted into flagellin, this system facilitates expression of random peptides in a conformationally constrained manner readily accessible on the flagellar surface. The random peptide library has been applied in antibody epitope mapping and is suitable for biopanning procedures in the study of ligand-receptor interactions. Many bacterial adhesins are of complex nature and thereby difficult to analyse by conventional methods. Direct flagella display has proven to be applicable also in bacterial adhesion technology since large fragments, up to 302 amino acid residues in length, of bacterial adhesins can be functionally expressed as fusions to flagellin. Hybrid flagella are easily purified and can easily be analysed for binding to various targets, such as immobilized proteins, tissue sections, as well as cell cultures.

Adhesins, Bacterial↗

Monoclonal antibodies directed against the flagella of Campylobacter jejuni: production, characterization and lack of effect on the colonization of infant mice.

Eight monoclonal antibodies have been derived from Balb/c mice hyperimmunized with the purified flagella from Campylobacter jejuni strain 81116. These monoclonal antibodies are directed against flagella as demonstrated by reaction in ELISA against flagellate and aflagellate antigens, radio-immunoprecipitation and electro-immunoblotting techniques. Some of the antibodies react with a 60K minor protein as well as the 62K flagella protein. This protein may be related to an antigen expressed on the surface of the organism and detectable by immunogold labelling with one of the monoclonal antibodies. None of the antibodies causes the aggregation of bacteria or inhibits bacterial motility, unlike polyclonal anti-flagella antiserum. Moreover, none of the antibodies tested protected infant mice from colonization with C. jejuni strain 81116 even though partial protection (28%) was observed with syngeneic anti-flagella anti-serum. Absence of protection is probably due to the cryptic nature of the flagella epitopes investigated or lack of antibody activity in the gastrointestinal tract.

Animals↗

The role of fimbriae and flagella in the colonization, invasion and persistence of Escherichia coli O78:K80 in the day-old-chick model.

To understand the role of flagella and fimbriae of Escherichia coli O78:K80 in avian colibacillosis, day-old chicks were dosed orally with defined afimbriate and or aflagellate mutants and colonization, invasion and persistence compared with that of the wild-type. In an invasion model, chicks were dosed with 1 x 10(5) c.f.u. of a single strain and mutants defective for type 1 fimbriae, curli fimbriae or flagella colonized livers by 24 h although the numbers of bacteria present were significantly less than the wild-type. Mutants colonized between 50 and 75% of spleens whereas the wild-type colonized 100% of spleens. Additionally, the numbers of mutant bacteria in colonized spleens were significantly less than the wild-type. Surprisingly, mutants defective for the elaboration of more than one appendage were no more attenuated than single mutants. In a persistence model, chicks were dosed with 1 x 10(2) c.f.u. of a single strain and mutants defective for type 1 or curli or flagella or any combination thereof persisted as assessed by cloacal swabbing for 5 weeks of the experiment less well than the wild-type. In an additional persistence model, chicks were dosed with 5 x 10(2) c.f.u. of each of wild-type and one mutant together. All mutants were significantly less persistent than the wild-type (P < 0.001) and one mutant which lacked type 1, curli and flagella, was eliminated within 2 weeks. Analysis of the trends of elimination indicated that flagella contributed to persistence more than curli, which contributed more than type 1 fimbriae. Here was evidence for a major role in colonization, invasion and persistence played by type 1, curli and flagella.

Animals↗

Intraflagellar transport (IFT) during assembly and disassembly of Chlamydomonas flagella.

Intraflagellar transport (IFT) of particles along flagellar microtubules is required for the assembly and maintenance of eukaryotic flagella and cilia. In Chlamydomonas, anterograde and retrograde particles viewed by light microscopy average 0.12-microm and 0.06-microm diameter, respectively. Examination of IFT particle structure in growing flagella by electron microscopy revealed similar size aggregates composed of small particles linked to each other and to the membrane and microtubules. To determine the relationship between the number of particles and flagellar length, the rate and frequency of IFT particle movement was measured in nongrowing, growing, and shortening flagella. In all flagella, anterograde and retrograde IFT averaged 1.9 microm/s and 2.7 microm/s, respectively, but retrograde IFT was significantly slower in flagella shorter than 4 mum. The number of flagellar IFT particles was not fixed, but depended on flagellar length. Pauses in IFT particle entry into flagella suggest the presence of a periodic "gate" that permits up to 4 particles/s to enter a flagellum.

Animals↗

Basal bodies of bacterial flagella in Proteus mirabilis. I. Electron microscopy of sectioned material.

Years ago (16, 18, 19), in a study of shadowed preparations of Proteus vulgaris that had been autolyzed in the cold, the observation was made that the flagella arose from basal bodies. However, recently (3, 7, 24, 33) doubt has been cast on the conclusion that the flagella of bacteria emerge from sizable basal bodies. This problem has, therefore, been reinvestigated with actively developing cultures of Proteus mirabilis, the cell walls of which had been expanded slightly by exposure to penicillin. Two techniques were applied: ultramicrotomy, and negative staining of whole mount preparations. This paper deals with the thin sections of bacteria after the usual fixation technique had been altered slightly: the cells were embedded in agar prior to their fixation and further processing. The flagella then remained attached to the cells and were seen to extend between the cell wall and the plasma membrane. Occasionally, the flagella appeared to be anchored in the cell by means of a hook-shaped ending. In sections of cells rich in cytoplasm, the basal bodies are particularly difficult to visualize due to their small size (25 to 45 mmicro) and the lack of properties that would enable one to distinguish them from the ribonucleoprotein structures; in addition, their boundary appears to be delicate. However, when the cytoplasm is sparse in the cells, either naturally or as a result of osmotic shocking in distilled water, the flagella can be observed to emerge from rounded structures approximately 25 to 45 mmicro wide. Contrary to a previous suggestion (21), the flagella do not terminate in the peripheral sites of reduced tellurite, i.e. the chondrioids. The observations in this part of the study agree with those described in the following paper (15) dealing with negatively stained preparations.

Cell Membrane↗

Endogenous glycosyltransferases glucosylate lipids in flagella of Euglena.

Flagella, intact deflagellated cells and isolated cell surfaces of the unicell , Euglena were separately assayed for glycosyltransferase activity by incubating these fractions with uridine diphosphate-[3H]glucose and isolating radiolabeled products. Most of the label was incorporated into lipophilic products, soluble in chloroform/methanol, which could be separated via thin layer chromatography or LH-60 chromatography into four distinct classes. The most polar of these products was extracted from flagella and purified by column chromatography for use as an in vitro substrate to identify flagella-associated glycosyltransferases. After flagella were treated with the detergent CHAPS , a soluble fraction was removed that was capable of glycosylation in solution. The glycosyltransferase(s) responsible for this activity were further enriched on sucrose or fructose gradients and ultimately identified on acrylamide gels through the combined use of nondenaturing gels, dial-[3H]uridine diphosphate binding, and fluorography. The enzyme had an apparent monomer molecular weight of 32,000 and consisted of four or fewer subunits. The occurrence of endogenous glycosyltransferase(s) in flagella suggests that modifications and/or assembly of the flagella surface can take place in situ in this organism.

Euglena↗

A flagella-less mutant of Borrelia burgdorferi as a live attenuated vaccine in the murine model of Lyme disease.

The immunogenicity and protective efficacy of an attenuated isolate of Borrelia burgdorferi, the agent of Lyme disease, were evaluated. An isogenic pair of isolates of strain HB19 differed in the expression of flagella; neither produced systemic infection or persisted in the skin of mice. In a comparison of intradermally administered live flagella-bearing and flagella-less cells, the flagella-less isolate was equal to or superior to the flagella-bearing wild type in eliciting growth-inhibiting antibodies and preventing infection in mice. In a comparison of live and killed flagella-less cells, immune responses to live cells were superior to those to killed cells, as assessed by ELISA, growth inhibition assay, and infectious challenge. The dose protecting 50% of mice was 10(3.8) and 10(5.2) for live and killed cells, respectively (P < .05).

Animals↗

Antigenicity of lateral flagella of Vibrio parahaemolyticus: existence of two distinct antigenic determinants in a flagellum.

Cells of Vibrio parahaemolyticus treated with Formalin agglutinated with anti-lateral flagella antiserum. On the basis of agglutination tests, antigens of lateral flagella were divided into three groups. HL1, HL2, and HL3. However, in gel diffusion tests, flagellins prepared from strains belonging to different groups showed a common antigenicity. It is assumed that these results are due to the existence of two distinct antigenic determinants in the lateral flagella. One of them exists on the surfaces of the flagella and is responsible for H-agglutination, and the other exists inside the flagella and is exposed when the flagella are solubilized to flagellin monomers.

Agglutination Tests↗