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1
Kanbe, Masaomi, Jin Yagasaki, Susanne Zehner, Michael Göttfert e Shin-Ichi Aizawa. "Characterization of Two Sets of Subpolar Flagella in Bradyrhizobium japonicum". Journal of Bacteriology 189, n. 3 (10 novembre 2006): 1083–89. http://dx.doi.org/10.1128/jb.01405-06.
Testo completoAbstract (sommario):
ABSTRACT Bradyrhizobium japonicum is one of the soil bacteria that form nodules on soybean roots. The cell has two sets of flagellar systems, one thick flagellum and a few thin flagella, uniquely growing at subpolar positions. The thick flagellum appears to be semicoiled in morphology, and the thin flagella were in a tight-curly form as observed by dark-field microscopy. Flagellin genes were identified from the amino acid sequence of each flagellin. Flagellar genes for the thick flagellum are scattered into several clusters on the genome, while those genes for the thin flagellum are compactly organized in one cluster. Both types of flagella are powered by proton-driven motors. The swimming propulsion is supplied mainly by the thick flagellum. B. japonicum flagellar systems resemble the polar-lateral flagellar systems of Vibrio species but differ in several aspects.
2
Campodónico, Victoria L., Nicolás J. Llosa, Martha Grout, Gerd Döring, Tomás Maira-Litrán e Gerald B. Pier. "Evaluation of Flagella and Flagellin of Pseudomonas aeruginosa as Vaccines". Infection and Immunity 78, n. 2 (7 dicembre 2009): 746–55. http://dx.doi.org/10.1128/iai.00806-09.
Testo completoAbstract (sommario):
ABSTRACT Pseudomonas aeruginosa is a serious pathogen in hospitalized, immunocompromised, and cystic fibrosis (CF) patients. P. aeruginosa is motile via a single polar flagellum made of polymerized flagellin proteins differentiated into two major serotypes: a and b. Antibodies to flagella delay onset of infection in CF patients, but whether immunity to polymeric flagella and that to monomeric flagellin are comparable has not been addressed, nor has the question of whether such antibodies might negatively impact Toll-like receptor 5 (TLR5) activation, an important component of innate immunity to P. aeruginosa. We compared immunization with flagella and that with flagellin for in vitro effects on motility, opsonic killing, and protective efficacy using a mouse pneumonia model. Antibodies to flagella were superior to antibodies to flagellin at inhibiting motility, promoting opsonic killing, and mediating protection against P. aeruginosa pneumonia in mice. Protection against the flagellar type strains PAK and PA01 was maximal, but it was only marginal against motile clinical isolates from flagellum-immunized CF patients who nonetheless became colonized with P. aeruginosa. Purified flagellin was a more potent activator of TLR5 than were flagella and also elicited higher TLR5-neutralizing antibodies than did immunization with flagella. Antibody to type a but not type b flagella or flagellin inhibited TLR5 activation by whole bacterial cells. Overall, intact flagella appear to be superior for generating immunity to P. aeruginosa, and flagellin monomers might induce antibodies capable of neutralizing innate immunity due to TLR5 activation, but solid immunity to P. aeruginosa based on flagellar antigens may require additional components beyond type a and type b proteins from prototype strains.
3
Marathe, Sandhya Amol, Arjun Balakrishnan, Vidya Devi Negi, Deepika Sakorey, Nagasuma Chandra e Dipshikha Chakravortty. "Curcumin Reduces the Motility of Salmonella enterica Serovar Typhimurium by Binding to the Flagella, Thereby Leading to Flagellar Fragility and Shedding". Journal of Bacteriology 198, n. 13 (18 aprile 2016): 1798–811. http://dx.doi.org/10.1128/jb.00092-16.
Testo completoAbstract (sommario):
ABSTRACTOne of the important virulence properties of the pathogen is its ability to travel to a favorable environment, cross the viscous mucus barrier (intestinal barrier for enteric pathogens), and reach the epithelia to initiate pathogenesis with the help of an appendage, like flagella. Nonetheless, flagella can act as an “Achilles heel,” revealing the pathogen's presence to the host through the stimulation of innate and adaptive immune responses. We assessed whether curcumin, a dietary polyphenol, could alter the motility ofSalmonella, a foodborne pathogen. It reduced the motility ofSalmonella entericaserovar Typhimurium by shortening the length of the flagellar filament (from ∼8 μm to ∼5 μm) and decreasing its density (4 or 5 flagella/bacterium instead of 8 or 9 flagella/bacterium). Upon curcumin treatment, the percentage of flagellated bacteria declined from ∼84% to 59%. However, no change was detected in the expression of the flagellin gene and protein. A fluorescence binding assay demonstrated binding of curcumin to the flagellar filament. This might make the filament fragile, breaking it into smaller fragments. Computational analysis predicted the binding of curcumin, its analogues, and its degraded products to a flagellin molecule at an interface between domains D1 and D2. Site-directed mutagenesis and a fluorescence binding assay confirmed the binding of curcumin to flagellin at residues ASN120, ASP123, ASN163, SER164, ASN173, and GLN175.IMPORTANCEThis work, to our knowledge the first report of its kind, examines how curcumin targets flagellar density and affects the pathogenesis of bacteria. We found that curcumin does not affect any of the flagellar synthesis genes. Instead, it binds to the flagellum and makes it fragile. It increases the torsional stress on the flagellar filament that then breaks, leaving fewer flagella around the bacteria. Flagella, which are crucial ligands for Toll-like receptor 5, are some of the most important appendages ofSalmonella. Curcumin is an important component of turmeric, which is a major spice used in Asian cooking. The loss of flagella can, in turn, change the pathogenesis of bacteria, making them more robust and fit in the host.
4
Iino, T., Tomoko Oguchi e T. Kuroiwa. "Polymorphism in a Flagellar-shape Mutant of Salmonella typhimurium". Microbiology 81, n. 1 (1 gennaio 2000): 37–45. http://dx.doi.org/10.1099/00221287-81-1-37.
Testo completoAbstract (sommario):
A flagellar-shape mutant, designated ‘polymorphous’, was isolated from a normal flagella strain of Salmonella typhimurium. The mutant produces normal flagella in phase 1 and polymorphous flagella in phase 2. The polymorphous flagella are either straight or possess one of the four distinct wave-forms, namely M, S, N or C, when observed with an electron microscope after negative staining with phosphotungstic acid or uranyl acetate. Conversions between the four wave-forms were found to be brought about mainly by a change in the degree of twisting of longitudinal strands around the axis of a flagella filament, without marked change in the relative lengths of the outermost and innermost strands. The major fraction of the polymorphous mutant flagella showed the N-form under any conditions of specimen preparation. The remaining four forms appeared as minor fractions in various proportions. Specimens fixed with formalin showed less pronounced polymorphism than unfixed ones. Negative staining with uranyl acetate was more effective than with phosphotungstic acid for observing polymorphism. Even though more than one form appeared among the polymorphous flagella, each individual flagellum comprised a single form except for a rare coexistence of S and N. The same form of flagella tended to coexist in a bacterium in a heteromorphously flagellated cell population. It was concluded that the conformation and arrangement of the flagellin molecules responsible for wave-form result from strong mutual interactions between the neighbouring molecules along the flagellar filaments and also, to a lesser extent, between the neighbouring filaments in a flagellar bundle, as well as being influenced by the physico-chemical environment.
5
Bardy, Sonia L., Takahisa Mori, Kaoru Komoriya, Shin-Ichi Aizawa e Ken F. Jarrell. "Identification and Localization of Flagellins FlaA and FlaB3 within Flagella of Methanococcus voltae". Journal of Bacteriology 184, n. 19 (1 ottobre 2002): 5223–33. http://dx.doi.org/10.1128/jb.184.19.5223-5233.2002.
Testo completoAbstract (sommario):
ABSTRACT Methanococcus voltae possesses four flagellin genes, two of which (flaB1 and flaB2) have previously been reported to encode major components of the flagellar filament. The remaining two flagellin genes, flaA and flaB3, are transcribed at lower levels, and the corresponding proteins remained undetected prior to this work. Electron microscopy examination of flagella isolated by detergent extraction of whole cells revealed a curved, hook-like region of varying length at the end of a long filament. Enrichment of the curved region of the flagella resulted in the identification of FlaB3 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and N-terminal sequencing, and the localization of this flagellin to the cell-proximal portion of the flagellum was confirmed through immunoblotting and immunoelectron microscopy with FlaB3-specific antibodies, indicating that FlaB3 likely composes the curved portion of the flagella. This could represent a unique case of a flagellin performing the role of the bacterial hook protein. FlaA-specific antibodies were used in immunoblotting to determine that FlaA is found throughout the flagellar filament. M. voltae cells were transformed with a modified flaA gene containing a hemagglutinin (HA) tag introduced into the variable region. Transformants that had replaced the wild-type copy of the flaA gene with the HA-tagged version incorporated the HA-tagged version of FlaA into flagella which appeared normal by electron microscopy.
6
del Campo, Ana Martínez, Teresa Ballado, Javier de la Mora, Sebastian Poggio, Laura Camarena e Georges Dreyfus. "Chemotactic Control of the Two Flagellar Systems of Rhodobacter sphaeroides Is Mediated by Different Sets of CheY and FliM Proteins". Journal of Bacteriology 189, n. 22 (21 settembre 2007): 8397–401. http://dx.doi.org/10.1128/jb.00730-07.
Testo completoAbstract (sommario):
ABSTRACT Rhodobacter sphaeroides expresses two different flagellar systems, a subpolar flagellum (fla1) and multiple polar flagella (fla2). These structures are encoded by different sets of flagellar genes. The chemotactic control of the subpolar flagellum (fla1) is mediated by three of the six different CheY proteins (CheY6, CheY4, or CheY3). We show evidence that CheY1, CheY2, and CheY5 control the chemotactic behavior mediated by fla2 flagella and that RSP6099 encodes the fla2 FliM protein.
7
Rabaan, Ali A., Ioannis Gryllos, Juan M. Tomás e Jonathan G. Shaw. "Motility and the Polar Flagellum Are Required for Aeromonas caviae Adherence to HEp-2 Cells". Infection and Immunity 69, n. 7 (1 luglio 2001): 4257–67. http://dx.doi.org/10.1128/iai.69.7.4257-4267.2001.
Testo completoAbstract (sommario):
ABSTRACT Aeromonas caviae is increasingly being recognized as a cause of gastroenteritis, especially among the young. The adherence of aeromonads to human epithelial cells in vitro has been correlated with enteropathogenicity, but the mechanism is far from well understood. Initial investigations demonstrated that adherence of A. caviae to HEp-2 cells was significantly reduced by either pretreating bacterial cells with an antipolar flagellin antibody or by pretreating HEp-2 cells with partially purified flagella. To precisely define the role of the polar flagellum in aeromonad adherence, we isolated the A. caviae polar flagellin locus and identified five polar flagellar genes, in the order flaA, flaB, flaG, flaH, and flaJ. Each gene was inactivated using a kanamycin resistance cartridge that ensures the transcription of downstream genes, and the resulting mutants were tested for motility, flagellin expression, and adherence to HEp-2 cells. N-terminal amino acid sequencing, mutant analysis, and Western blotting demonstrated that A. caviae has a complex flagellum filament composed of two flagellin subunits encoded by flaAand flaB. The predicted molecular mass of both flagellins was ∼31,700 Da; however, their molecular mass estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was ∼35,500 Da. This aberrant migration was thought to be due to their glycosylation, since the proteins were reactive in glycosyl group detection assays. Single mutations in either flaA orflaB did not result in loss of flagella but did result in decreased motility and adherence by approximately 50%. Mutation offlaH, flaJ, or both flagellin genes resulted in the complete loss of motility, flagellin expression, and adherence. However, mutation of flaG did not affect motility but did significantly reduce the level of adherence. Centrifugation of the flagellate mutants (flaA, flaB, and flaG) onto the cell monolayers did not increase adherence, whereas centrifugation of the aflagellate mutants (flaH, flaJ, and flaA flaB) increased adherence slightly. We conclude that maximum adherence of A. caviae to human epithelial cells in vitro requires motility and optimal flagellar function.
8
Kirov, Sylvia M., Bronwen C. Tassell, Annalese B. T. Semmler, Lisa A. O’Donovan, Ali A. Rabaan e Jonathan G. Shaw. "Lateral Flagella and Swarming Motility in Aeromonas Species". Journal of Bacteriology 184, n. 2 (15 gennaio 2002): 547–55. http://dx.doi.org/10.1128/jb.184.2.547-555.2002.
Testo completoAbstract (sommario):
ABSTRACT Swarming motility, a flagellum-dependent behavior that allows bacteria to move over solid surfaces, has been implicated in biofilm formation and bacterial virulence. In this study, light and electron microscopic analyses and genetic and functional investigations have shown that at least 50% of Aeromonas isolates from the species most commonly associated with diarrheal illness produce lateral flagella which mediate swarming motility. Aeromonas lateral flagella were optimally produced when bacteria were grown on solid medium for ≈8 h. Transmission and thin-section electron microscopy confirmed that these flagella do not possess a sheath structure. Southern analysis of Aeromonas reference strains and strains of mesophilic species (n = 84, varied sources and geographic regions) with a probe designed to detect lateral flagellin genes (lafA1 and lafA2) showed there was no marked species association of laf distribution. Approximately 50% of these strains hybridized strongly with the probe, in good agreement with the expression studies. We established a reproducible swarming assay (0.5% Eiken agar in Difco broth, 30°C) for Aeromonas spp. The laf-positive strains exhibited vigorous swarming motility, whereas laf-negative strains grew but showed no movement from the inoculation site. Light and scanning electron microscopic investigations revealed that lateral flagella formed bacterium-bacterium linkages on the agar surface. Strains of an Aeromonas caviae isolate in which lateral flagellum expression was abrogated by specific mutations in flagellar genes did not swarm, proving conclusively that lateral flagella are required for the surface movement. Whether lateral flagella and swarming motility contribute to Aeromonas intestinal colonization and virulence remains to be determined.
9
Canals, Rocío, Maria Altarriba, Silvia Vilches, Gavin Horsburgh, Jonathan G. Shaw, Juan M. Tomás e Susana Merino. "Analysis of the Lateral Flagellar Gene System of Aeromonas hydrophila AH-3". Journal of Bacteriology 188, n. 3 (1 febbraio 2006): 852–62. http://dx.doi.org/10.1128/jb.188.3.852-862.2006.
Testo completoAbstract (sommario):
ABSTRACT Mesophilic Aeromonas strains express a polar flagellum in all culture conditions, and certain strains produce lateral flagella on semisolid media or on surfaces. Although Aeromonas lateral flagella have been described as a colonization factor, little is known about their organization and expression. Here we characterized the complete lateral flagellar gene cluster of Aeromonas hydrophila AH-3 containing 38 genes, 9 of which (lafA-U) have been reported previously. Among the flgL L and lafA structural genes we found a modification accessory factor gene (maf-5) that is involved in formation of lateral flagella; this is the first time that such a gene has been described for lateral flagellar gene systems. All Aeromonas lateral flagellar genes were located in a unique chromosomal region, in contrast to Vibrio parahaemolyticus, in which the analogous genes are distributed in two different chromosomal regions. In A. hydrophila mutations in flhA L, lafK, fliJ L, flgN L, flgE L, and maf-5 resulted in a loss of lateral flagella and reductions in adherence and biofilm formation, but they did not affect polar flagellum synthesis. Furthermore, we also cloned and sequenced the A. hydrophila AH-3 alternative sigma factor σ54 (rpoN); mutation of this factor suggested that it is involved in expression of both types of flagella.
10
Yen, Jiun Y., Katherine M. Broadway e Birgit E. Scharf. "Minimum Requirements of Flagellation and Motility for Infection of Agrobacterium sp. Strain H13-3 by Flagellotropic Bacteriophage 7-7-1". Applied and Environmental Microbiology 78, n. 20 (3 agosto 2012): 7216–22. http://dx.doi.org/10.1128/aem.01082-12.
Testo completoAbstract (sommario):
ABSTRACTThe flagellotropic phage 7-7-1 specifically adsorbs toAgrobacteriumsp. strain H13-3 (formerlyRhizobium lupiniH13-3) flagella for efficient host infection. TheAgrobacteriumsp. H13-3 flagellum is complex and consists of three flagellin proteins: the primary flagellin FlaA, which is essential for motility, and the secondary flagellins FlaB and FlaD, which have minor functions in motility. Using quantitative infectivity assays, we showed that absence of FlaD had no effect on phage infection, while absence of FlaB resulted in a 2.5-fold increase in infectivity. AflaAdeletion strain, which produces straight and severely truncated flagella, experienced a significantly reduced infectivity, similar to that of aflaB flaDstrain, which produces a low number of straight flagella. A strain lacking all three flagellin genes is phage resistant. In addition to flagellation, flagellar rotation is required for infection. A strain that is nonmotile due to an in-frame deletion in the gene encoding the motor component MotA is resistant to phage infection. We also generated two strains with point mutations in themotAgene resulting in replacement of the conserved charged residue Glu98, which is important for modulation of rotary speed. A change to the neutral Gln caused the flagellar motor to rotate at a constant high speed, allowing a 2.2-fold-enhanced infectivity. A change to the positively charged Lys caused a jiggly motility phenotype with very slow flagellar rotation, which significantly reduced the efficiency of infection. In conclusion, flagellar number and length, as well as speed of flagellar rotation, are important determinants for infection by phage 7-7-1.
11
Fedorov, Oleg V., Michael G. Pyatibratov, Alla S. Kostyukova, Natalja K. Osina e Valery Yu Tarasov. "Protofilament as a structural element of flagella of haloalkalophilic archaebacteria". Canadian Journal of Microbiology 40, n. 1 (1 gennaio 1994): 45–53. http://dx.doi.org/10.1139/m94-007.
Testo completoAbstract (sommario):
Flagella of the haloalkalophilic archaebacterium Natronobacterium magadii were purified and characterized. The diameter of the flagella was 10 nm. It was shown that the flagella consist of four major proteins with molecular weights of 105 000, 60 000, 59 000, and 45 000. With decreasing NaCl concentration, the flagella dissociated into protofilaments. The structure of dissociated flagella and individual flagellins was studied by limited proteolysis. It was found that proteolytic cleavage of flagellins in dissociated flagella into high molecular weight fragments (about 40 000) did not lead to protofilament degradation. It was shown that the most stable fragment is formed from the 60 000 molecular weight flagellin. Cleavage of this fragment led to complete disappearance of protofilaments. On the basis of the data obtained, possible principles of archaebacterial flagellar construction are discussed.Key words: flagellin, archaebacteria, protofilaments, Natronobacterium magadii.
12
Garrett, Edward S., Demetra Perlegas e Daniel J. Wozniak. "Negative Control of Flagellum Synthesis in Pseudomonas aeruginosa Is Modulated by the Alternative Sigma Factor AlgT (AlgU)". Journal of Bacteriology 181, n. 23 (1 dicembre 1999): 7401–4. http://dx.doi.org/10.1128/jb.181.23.7401-7404.1999.
Testo completoAbstract (sommario):
ABSTRACT Many respiratory isolates of Pseudomonas aeruginosafrom cystic fibrosis patients are mucoid (alginate producing) yet lack flagella. It was hypothesized that an alginate regulator inhibits flagellar gene expression. Mutations in algB,algR, and algT resulted in nonmucoid derivatives, yet algT mutants expressed flagella. AlgT-dependent control of flagellum synthesis occurred through inhibition of fliC but not rpoN transcription.
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Gray, Victoria L., Michael O'Reilly, Carsten T. Müller, Ian D. Watkins e David Lloyd. "Low tyrosine content of growth media yields aflagellate Salmonella enterica serovar Typhimurium". Microbiology 152, n. 1 (1 gennaio 2006): 23–28. http://dx.doi.org/10.1099/mic.0.28442-0.
Testo completoAbstract (sommario):
Identification of Salmonella serotypes is based on flagellar and somatic antigens. The absence of flagella may consequently affect complete identification of the serotype; here it is shown that Salmonella enterica serovar Typhimurium exhibits morphological differences dependent on the peptone constituents of the culture medium. Aflagellate salmonella were produced in certain media where the nutritional ingredient was casein-based peptone or gelatin-based peptone; in gelatin-based peptone, aggregates of salmonella were observed. However, in media containing soy-based peptone as the primary nutrient, salmonella displayed a normal flagellated morphology. Transfer of aflagellate salmonella from nutritionally poor media, with casein- or gelatin-based peptone, into rich nutrient broth allowed flagella synthesis, indicating that the aflagellate form is still able to produce flagella. Amino acid sequencing of the peptones producing aflagellate organisms showed a relatively low tyrosine concentration: only 0·03±0·01 g l−1 for gelatin-based buffered peptone water, compared to 0·21±0·01 for soy-based buffered peptone water. Tyrosine is essential for flagellin, which is the subunit of the salmonella flagellar filament. The addition of 200 μM tyrosine to casein-based peptone media produced flagellate salmonella; 2 mM glucose was needed in addition to tyrosine to achieve a similar morphology in gelatin-based media. Therefore, culture media containing less than 1·20 g tyrosine l−1, and of limited carbohydrate source, when used for serological testing of clinical isolates, may result in an incomplete serological identification.
14
Tasteyre, Albert, Marie-Claude Barc, Anne Collignon, Helene Boureau e Tuomo Karjalainen. "Role of FliC and FliD Flagellar Proteins ofClostridium difficile in Adherence and Gut Colonization". Infection and Immunity 69, n. 12 (1 dicembre 2001): 7937–40. http://dx.doi.org/10.1128/iai.69.12.7937-7940.2001.
Testo completoAbstract (sommario):
ABSTRACT In vitro and in vivo adhesive properties of flagella and recombinant flagellin FliC and flagellar cap FliD proteins ofClostridium difficile were analyzed. FliC, FliD, and crude flagella adhered in vitro to axenic mouse cecal mucus. Radiolabeled cultured cells bound to a high degree to FliD and weakly to flagella deposited on a membrane. The tissue association in the mouse cecum of a nonflagellated strain was 10-fold lower than that of a flagellated strain belonging to the same serogroup, confirming the role of flagella in adherence.
15
Alexandre, Gladys, René Rohr e René Bally. "A Phase Variant of Azospirillum lipoferum Lacks a Polar Flagellum and Constitutively Expresses Mechanosensing Lateral Flagella". Applied and Environmental Microbiology 65, n. 10 (1 ottobre 1999): 4701–4. http://dx.doi.org/10.1128/aem.65.10.4701-4704.1999.
Testo completoAbstract (sommario):
ABSTRACT Flagellation of a nonswimming variant of the mixed flagellated bacterium Azospirillum lipoferum 4B was characterized by electron microscopy, and polyclonal antibodies were raised against polar and lateral flagellins. The variant cells lacked a polar flagellum due to a defect in flagellin synthesis and constitutively expressed lateral flagella. The variant cells were able to respond to conditions that restricted the rotation of lateral flagella by producing more lateral flagella, suggesting that the lateral flagella, as well as the polar flagellum, are mechanosensing.
16
Yoon, Sang Sun, e John J. Mekalanos. "Decreased Potency of the Vibrio cholerae Sheathed Flagellum To Trigger Host Innate Immunity". Infection and Immunity 76, n. 3 (3 gennaio 2008): 1282–88. http://dx.doi.org/10.1128/iai.00736-07.
Testo completoAbstract (sommario):
ABSTRACT Vibrio cholerae is a monoflagellated gram-negative bacterium that causes the severe diarrheal disease cholera. In contrast to Salmonella enterica serovar Typhimurium infection, which is accompanied by both acute diarrhea and high-level inflammation, V. cholerae infection is largely noninflammatory in human hosts. Bacterial flagella are composed of flagellin, a highly conserved protein that is also a target of the innate immune response. Because the V. cholerae flagellum is covered by a sheath, we hypothesized that it might be less prone to activation of the innate immune response than nonsheathed flagella, such as those produced by Salmonella serovar Typhimurium. Indeed, compared with Salmonella serovar Typhimurium flagella, V. cholerae flagella demonstrated significantly reduced NF-κB activation in A549 human pulmonary epithelial cells. However, V. cholerae flagellin monomers, FlaD and FlaC, were almost equally potent with purified FliC, a monomer derived from Salmonella serovar Typhimurium flagella, in NF-κB activation. Heat- and acid-induced dissociation assays showed that Salmonella serovar Typhimurium flagella disassembled far more readily into monomeric flagellins than V. cholerae flagella, suggesting that the differential levels of NF-κB activation by V. cholerae and Salmonella serovar Typhimurium flagella are likely attributable to the difference in their flagellin shedding. Our results suggest that monomer dissociation of V. cholerae flagella is suppressed likely due to the presence of the sheath and that this unique structural feature of V. cholerae flagella may have evolved as a strategy to evade flagellin-triggered host innate immune responses in various host species.
17
Kim, Yun-Kyeong, e Linda L. McCarter. "Analysis of the Polar Flagellar Gene System ofVibrio parahaemolyticus". Journal of Bacteriology 182, n. 13 (1 luglio 2000): 3693–704. http://dx.doi.org/10.1128/jb.182.13.3693-3704.2000.
Testo completoAbstract (sommario):
ABSTRACT Vibrio parahaemolyticus has dual flagellar systems adapted for locomotion under different circumstances. A single, sheathed polar flagellum propels the swimmer cell in liquid environments. Numerous unsheathed lateral flagella move the swarmer cell over surfaces. The polar flagellum is produced continuously, whereas the synthesis of lateral flagella is induced under conditions that impede the function of the polar flagellum, e.g., in viscous environments or on surfaces. Thus, the organism possesses two large gene networks that orchestrate polar and lateral flagellar gene expression and assembly. In addition, the polar flagellum functions as a mechanosensor controlling lateral gene expression. In order to gain insight into the genetic circuitry controlling motility and surface sensing, we have sought to define the polar flagellar gene system. The hierarchy of regulation appears to be different from the polar system of Caulobacter crescentus or the peritrichous system of enteric bacteria but is pertinent to many Vibrio andPseudomonas species. The gene identity and organization of 60 potential flagellar and chemotaxis genes are described. Conserved sequences are defined for two classes of polar flagellar promoters. Phenotypic and genotypic analysis of mutant strains with defects in swimming motility coupled with primer extension analysis of flagellar and chemotaxis transcription provides insight into the polar flagellar organelle, its assembly, and regulation of gene expression.
18
Filip’echeva, Yulia A., Andrei V. Shelud’ko, Alexei G. Prilipov, Gennady L. Burygin, Elizaveta M. Telesheva, Stella S. Yevstigneyeva, Marina P. Chernyshova, Lilia P. Petrova e Elena I. Katsy. "Plasmid AZOBR_p1-borne fabG gene for putative 3-oxoacyl-[acyl-carrier protein] reductase is essential for proper assembly and work of the dual flagellar system in the alphaproteobacterium Azospirillum brasilense Sp245". Canadian Journal of Microbiology 64, n. 2 (febbraio 2018): 107–18. http://dx.doi.org/10.1139/cjm-2017-0561.
Testo completoAbstract (sommario):
Azospirillum brasilense can swim and swarm owing to the activity of a constitutive polar flagellum (Fla) and inducible lateral flagella (Laf), respectively. Experimental data on the regulation of the Fla and Laf assembly in azospirilla are scarce. Here, the coding sequence (CDS) AZOBR_p1160043 (fabG1) for a putative 3-oxoacyl-[acyl-carrier protein (ACP)] reductase was found essential for the construction of both types of flagella. In an immotile leaky Fla− Laf− fabG1::Omegon-Km mutant, Sp245.1610, defects in flagellation and motility were fully complemented by expressing the CDS AZOBR_p1160043 from plasmid pRK415. When pRK415 with the cloned CDS AZOBR_p1160045 (fliC) for a putative 65.2 kDa Sp245 Fla flagellin was transferred into the Sp245.1610 cells, the bacteria also became able to assemble a motile single flagellum. Some cells, however, had unusual swimming behavior, probably because of the side location of the organelle. Although the assembly of Laf was not restored in Sp245.1610 (pRK415-p1160045), this strain was somewhat capable of swarming motility. We propose that the putative 3-oxoacyl-[ACP] reductase encoded by the CDS AZOBR_p1160043 plays a role in correct flagellar location in the cell envelope and (or) in flagellar modification(s), which are also required for the inducible construction of Laf and for proper swimming and swarming motility of A. brasilense Sp245.
19
Kirov, Sylvia M., Marika Castrisios e Jonathan G. Shaw. "Aeromonas Flagella (Polar and Lateral) Are Enterocyte Adhesins That Contribute to Biofilm Formation on Surfaces". Infection and Immunity 72, n. 4 (aprile 2004): 1939–45. http://dx.doi.org/10.1128/iai.72.4.1939-1945.2004.
Testo completoAbstract (sommario):
ABSTRACT Aeromonas spp. (gram-negative, aquatic bacteria which include enteropathogenic strains) have two distinct flagellar systems, namely a polar flagellum for swimming in liquid and multiple lateral flagella for swarming over surfaces. Only ∼60% of mesophilic strains can produce lateral flagella. To evaluate flagellar contributions to Aeromonas intestinal colonization, we compared polar and lateral flagellar mutant strains of a diarrheal isolate of Aeromonas caviae for the ability to adhere to the intestinal cell lines Henle 407 and Caco-2, which have the characteristic features of human intestinal enterocytes. Strains lacking polar flagella were virtually nonadherent to these cell lines, while loss of the lateral flagellum decreased adherence by ∼60% in comparison to the wild-type level. Motility mutants (unable to swim or swarm in agar assays) had adhesion levels of ∼50% of wild-type values, irrespective of their flagellar expression. Flagellar mutant strains were also evaluated for the ability to form biofilms in a borosilicate glass tube model which was optimized for Aeromonas spp. (broth inoculum, with a 16- to 20-h incubation at 37°C). All flagellar mutants showed a decreased ability to form biofilms (at least 30% lower than the wild type). For the chemotactic motility mutant cheA, biofilm formation decreased >80% from the wild-type level. The complementation of flagellar phenotypes (polar flagellar mutants) restored biofilms to wild-type levels. We concluded that both flagellar types are enterocyte adhesins and need to be fully functional for optimal biofilm formation.
20
Konishi, Manabu, Masaomi Kanbe, Jonathan L. McMurry e Shin-Ichi Aizawa. "Flagellar Formation in C-Ring-Defective Mutants by Overproduction of FliI, the ATPase Specific for Flagellar Type III Secretion". Journal of Bacteriology 191, n. 19 (31 luglio 2009): 6186–91. http://dx.doi.org/10.1128/jb.00601-09.
Testo completoAbstract (sommario):
ABSTRACT The flagellar cytoplasmic ring (C ring), which consists of three proteins, FliG, FliM, and FliN, is located on the cytoplasmic side of the flagellum. The C ring is a multifunctional structure necessary for flagellar protein secretion, torque generation, and switching of the rotational direction of the motor. The deletion of any one of the fliG, fliM, and fliN genes results in a Fla− phenotype. Here, we show that the overproduction of the flagellum-specific ATPase FliI overcomes the inability of basal bodies with partial C-ring structures to produce complete flagella. Flagella made upon FliI overproduction were paralyzed, indicating that an intact C ring is essential for motor function. In FliN- or FliM-deficient mutants, flagellum production was about 10% of the wild-type level, while it was only a few percent in FliG-deficient mutants, suggesting that the size of partial C rings affects the extent of flagellation. For flagella made in C-ring mutants, the hook length varied considerably, with many being markedly shorter or longer than that of the wild type. The broad distribution of hook lengths suggests that defective C rings cannot control the hook length as tightly as the wild type even though FliK and FlhB are both intact.
21
Poggio, Sebastian, Cei Abreu-Goodger, Salvador Fabela, Aurora Osorio, Georges Dreyfus, Pablo Vinuesa e Laura Camarena. "A Complete Set of Flagellar Genes Acquired by Horizontal Transfer Coexists with the Endogenous Flagellar System in Rhodobacter sphaeroides". Journal of Bacteriology 189, n. 8 (9 febbraio 2007): 3208–16. http://dx.doi.org/10.1128/jb.01681-06.
Testo completoAbstract (sommario):
ABSTRACT Bacteria swim in liquid environments by means of a complex rotating structure known as the flagellum. Approximately 40 proteins are required for the assembly and functionality of this structure. Rhodobacter sphaeroides has two flagellar systems. One of these systems has been shown to be functional and is required for the synthesis of the well-characterized single subpolar flagellum, while the other was found only after the genome sequence of this bacterium was completed. In this work we found that the second flagellar system of R. sphaeroides can be expressed and produces a functional flagellum. In many bacteria with two flagellar systems, one is required for swimming, while the other allows movement in denser environments by producing a large number of flagella over the entire cell surface. In contrast, the second flagellar system of R. sphaeroides produces polar flagella that are required for swimming. Expression of the second set of flagellar genes seems to be positively regulated under anaerobic growth conditions. Phylogenic analysis suggests that the flagellar system that was initially characterized was in fact acquired by horizontal transfer from a γ-proteobacterium, while the second flagellar system contains the native genes. Interestingly, other α-proteobacteria closely related to R. sphaeroides have also acquired a set of flagellar genes similar to the set found in R. sphaeroides, suggesting that a common ancestor received this gene cluster.
22
Parthasarathy, G., Y. Yao e K. S. Kim. "Flagella Promote Escherichia coli K1 Association with and Invasion of Human Brain Microvascular Endothelial Cells". Infection and Immunity 75, n. 6 (19 marzo 2007): 2937–45. http://dx.doi.org/10.1128/iai.01543-06.
Testo completoAbstract (sommario):
ABSTRACT Escherichia coli containing the K1 capsule is the leading cause of gram-negative meningitis, but the pathogenesis of this disease is not completely understood. Recent microarray experiments in which we compared the gene expression profile of E. coli K1 associated with human brain microvascular endothelial cells (HBMEC) to the gene expression profile of E. coli K1 not associated with HBMEC revealed that there was a threefold increase in the expression of the fliI gene, encoding an ATP synthase involved in flagellar synthesis and motility, in HBMEC-associated E. coli. In this study, we examined the role of flagella in E. coli K1 association with and invasion of HBMEC by constructing isogenic ΔflhDC, ΔfliI, ΔfliC, and ΔcheW mutants that represented each class of flagellar genes. Mutations that affected the flagellum structure and flagellum formation (ΔflhDC, ΔfliI, and ΔfliC) resulted in significant defects in motility, as well as in HBMEC association and invasion, compared to the characteristics of the wild-type strain when preparations were examined with or without centrifugation. Transcomplementation with the corresponding genes restored the levels of these mutants to the levels of the parent strain. These findings suggest that the HBMEC association and invasion defects of the mutants are most likely related to flagella and less likely due to their motility defects. This conclusion was supported by our demonstration that the cheW mutant was not motile but was able to associate with and invade HBMEC. In addition, purified recombinant flagellin reduced the association of the wild-type strain with HBMEC by ∼40%, while it had no effect on the fliC mutant's association with HBMEC. Together, these findings indicate that flagella promote E. coli K1 binding to HBMEC.
23
Sterzenbach, Torsten, Lucie Bartonickova, Wiebke Behrens, Birgit Brenneke, Jessika Schulze, Friederike Kops, Elaine Y. Chin et al. "Role of the Helicobacter hepaticus Flagellar Sigma Factor FliA in Gene Regulation and Murine Colonization". Journal of Bacteriology 190, n. 19 (8 agosto 2008): 6398–408. http://dx.doi.org/10.1128/jb.00626-08.
Testo completoAbstract (sommario):
ABSTRACT The enterohepatic Helicobacter species Helicobacter hepaticus colonizes the murine intestinal and hepatobiliary tract and is associated with chronic intestinal inflammation, gall stone formation, hepatitis, and hepatocellular carcinoma. Thus far, the role of H. hepaticus motility and flagella in intestinal colonization is unknown. In other, closely related bacteria, late flagellar genes are mainly regulated by the sigma factor FliA (σ28). We investigated the function of the H. hepaticus FliA in gene regulation, flagellar biosynthesis, motility, and murine colonization. Competitive microarray analysis of the wild type versus an isogenic fliA mutant revealed that 11 genes were significantly more highly expressed in wild-type bacteria and 2 genes were significantly more highly expressed in the fliA mutant. Most of these were flagellar genes, but four novel FliA-regulated genes of unknown function were identified. H. hepaticus possesses two identical copies of the gene encoding the FliA-dependent major flagellin subunit FlaA (open reading frames HH1364 and HH1653). We characterized the phenotypes of mutants in which fliA or one or both copies of the flaA gene were knocked out. flaA_1 flaA_2 double mutants and fliA mutants did not synthesize detectable amounts of FlaA and possessed severely truncated flagella. Also, both mutants were nonmotile and unable to colonize mice. Mutants with either flaA gene knocked out produced flagella morphologically similar to those of wild-type bacteria and expressed FlaA and FlaB. flaA_1 mutants which had flagella but displayed reduced motility did not colonize mice, indicating that motility is required for intestinal colonization by H. hepaticus and that the presence of flagella alone is not sufficient.
24
Redondo-Nieto, Miguel, Javier Lloret, Javiera Larenas, Emma Barahona, Ana Navazo, Francisco Martínez-Granero, Silvia Capdevila, Rafael Rivilla e Marta Martín. "Transcriptional Organization of the Region Encoding the Synthesis of the Flagellar Filament in Pseudomonas fluorescens". Journal of Bacteriology 190, n. 11 (28 marzo 2008): 4106–9. http://dx.doi.org/10.1128/jb.00178-08.
Testo completoAbstract (sommario):
ABSTRACT Pseudomonas fluorescens F113 is motile by means of type b flagella. Analysis of the region encoding the synthesis of the flagellar filament has shown a transcriptional organization different from that of type a flagella. Additionally to the promoters driving fliC, fliD, and fleQ expression, we have found promoters upstream of the flaG gene and the fliST operon. These promoters were functional in vivo. Both promoters have been mapped and appear to be dependent on the vegetative sigma factor and independent of FleQ, the master regulator of flagellum synthesis.
25
Senesi, Sonia, Emilia Ghelardi, Francesco Celandroni, Sara Salvetti, Eva Parisio e Alessandro Galizzi. "Surface-Associated Flagellum Formation and Swarming Differentiation in Bacillus subtilis Are Controlled by the ifm Locus". Journal of Bacteriology 186, n. 4 (15 febbraio 2004): 1158–64. http://dx.doi.org/10.1128/jb.186.4.1158-1164.2004.
Testo completoAbstract (sommario):
ABSTRACT Knowledge of the highly regulated processes governing the production of flagella in Bacillus subtilis is the result of several observations obtained from growing this microorganism in liquid cultures. No information is available regarding the regulation of flagellar formation in B. subtilis in response to contact with a solid surface. One of the best-characterized responses of flagellated eubacteria to surfaces is swarming motility, a coordinate cell differentiation process that allows collective movement of bacteria over solid substrates. This study describes the swarming ability of a B. subtilis hypermotile mutant harboring a mutation in the ifm locus that has long been known to affect the degree of flagellation and motility in liquid media. On solid media, the mutant produces elongated and hyperflagellated cells displaying a 10-fold increase in extracellular flagellin. In contrast to the mutant, the parental strain, as well as other laboratory strains carrying a wild-type ifm locus, fails to activate a swarm response. Furthermore, it stops to produce flagella when transferred from liquid to solid medium. Evidence is provided that the absence of flagella is due to the lack of flagellin gene expression. However, restoration of flagellin synthesis in cells overexpressing σD or carrying a deletion of flgM does not recover the ability to assemble flagella. Thus, the ifm gene plays a determinantal role in the ability of B. subtilis to contact with solid surfaces.
26
Shapiro, Jessica, Jessica Ingram e Karl A. Johnson. "Characterization of a Molecular Chaperone Present in the Eukaryotic Flagellum". Eukaryotic Cell 4, n. 9 (settembre 2005): 1591–94. http://dx.doi.org/10.1128/ec.4.9.1591-1594.2005.
Testo completoAbstract (sommario):
ABSTRACT Chlamydomonas flagella contain a molecular chaperone now identified as HSP70A, a major cytoplasmic isoform. HSP70A synthesis is upregulated by deflagellation, and its distribution in the flagellum overlaps with the IFT kinesin-II motor FLA10. HSP70A may chaperone flagellar proteins during transport, participating in the assembly and maintenance of the flagellum.
27
Li, Chunhao, Melanie Sal, Michael Marko e Nyles W. Charon. "Differential Regulation of the Multiple Flagellins in Spirochetes". Journal of Bacteriology 192, n. 10 (19 marzo 2010): 2596–603. http://dx.doi.org/10.1128/jb.01502-09.
Testo completoAbstract (sommario):
ABSTRACT The expression of flagellin genes in most bacteria is typically regulated by the flagellum-specific sigma28 factor FliA, and an anti-sigma28 factor, FlgM. However, the regulatory hierarchy in several bacteria that have multiple flagellins is more complex. In these bacteria, the flagellin genes are often transcribed by at least two different sigma factors. The flagellar filament in spirochetes consists of one to three FlaB core proteins and at least one FlaA sheath protein. Here, the genetically amenable bacterium Brachyspira hyodysenteriae was used as a model spirochete to investigate the regulation of its four flagellin genes, flaA, flaB1, flaB2, and flaB3. We found that the flaB1 and flaB2 genes are regulated by sigma28, whereas the flaA and flaB3 genes are controlled by sigma70. The analysis of a flagellar motor switch fliG mutant further supported this proposition; in the mutant, the transcription of flaB1 and flaB2 was inhibited, but that of flaA and flaB3 was not. In addition, the continued expression of flaA and flaB3 in the mutant resulted in the formation of incomplete flagellar filaments that were hollow tubes and consisted primarily of FlaA. Finally, our recent studies have shown that each flagellin unit contributes to the stiffness of the periplasmic flagella, and this stiffness directly correlates with motility. The regulatory mechanism identified here should allow spirochetes to change the relative ratio of these flagellin proteins and, concomitantly, vary the stiffness of their flagellar filament.
28
Lane, M. Chelsea, Virginia Lockatell, Greta Monterosso, Daniel Lamphier, Julia Weinert, J. Richard Hebel, David E. Johnson e Harry L. T. Mobley. "Role of Motility in the Colonization of Uropathogenic Escherichia coli in the Urinary Tract". Infection and Immunity 73, n. 11 (novembre 2005): 7644–56. http://dx.doi.org/10.1128/iai.73.11.7644-7656.2005.
Testo completoAbstract (sommario):
ABSTRACT Uropathogenic Escherichia coli (UPEC) causes most uncomplicated urinary tract infections (UTIs) in humans. Flagellum-mediated motility and chemotaxis have been suggested to contribute to virulence by enabling UPEC to escape host immune responses and disperse to new sites within the urinary tract. To evaluate their contribution to virulence, six separate flagellar mutations were constructed in UPEC strain CFT073. The mutants constructed were shown to have four different flagellar phenotypes: fliA and fliC mutants do not produce flagella; the flgM mutant has similar levels of extracellular flagellin as the wild type but exhibits less motility than the wild type; the motAB mutant is nonmotile; and the cheW and cheY mutants are motile but nonchemotactic. Virulence was assessed by transurethral independent challenges and cochallenges of CBA mice with the wild type and each mutant. CFU/ml of urine or CFU/g bladder or kidney was determined 3 days postinoculation for the independent challenges and at 6, 16, 48, 60, and 72 h postinoculation for the cochallenges. While these mutants colonized the urinary tract during independent challenge, each of the mutants was outcompeted by the wild-type strain to various degrees at specific time points during cochallenge. Altogether, these results suggest that flagella and flagellum-mediated motility/chemotaxis may not be absolutely required for virulence but that these traits contribute to the fitness of UPEC and therefore significantly enhance the pathogenesis of UTIs caused by UPEC.
29
de la Mora, Javier, Kaoru Uchida, Ana Martínez del Campo, Laura Camarena, Shin-Ichi Aizawa e Georges Dreyfus. "Structural Characterization of the Fla2 Flagellum of Rhodobacter sphaeroides". Journal of Bacteriology 197, n. 17 (29 giugno 2015): 2859–66. http://dx.doi.org/10.1128/jb.00170-15.
Testo completoAbstract (sommario):
ABSTRACTRhodobacter sphaeroidesis a free-living alphaproteobacterium that contains two clusters of functional flagellar genes in its genome: one acquired by horizontal gene transfer (fla1) and one that is endogenous (fla2). We have shown that the Fla2 system is normally quiescent and under certain conditions produces polar flagella, while the Fla1 system is always active and produces a single flagellum at a nonpolar position. In this work we purified and characterized the structure and analyzed the composition of the Fla2 flagellum. The number of polar filaments per cell is 4.6 on average. By comparison with the Fla1 flagellum, the prominent features of the ultra structure of the Fla2 HBB are the absence of an H ring, thick and long hooks, and a smoother zone at the hook-filament junction. The Fla2 helical filaments have a pitch of 2.64 μm and a diameter of 1.4 μm, which are smaller than those of the Fla1 filaments. Fla2 filaments undergo polymorphic transitionsin vitroand showed two polymorphs: curly (right-handed) and coiled. However,in vivoin free-swimming cells, we observed only a bundle of filaments, which should probably be left-handed. Together, our results indicate that Fla2 cell produces multiple right-handed polar flagella, which are not conventional but exceptional.IMPORTANCER. sphaeroidespossesses two functional sets of flagellar genes. The fla1 genes are normally expressed in the laboratory and were acquired by horizontal transfer. The fla2 genes are endogenous and are expressed in a Fla1−mutant grown phototrophically and in the absence of organic acids. The Fla1 system produces a single lateral or subpolar flagellum, and the Fla2 system produces multiple polar flagella. The two kinds of flagella are never expressed simultaneously, and both are used for swimming in liquid media. The two sets of genes are certainly ready for responding to specific environmental conditions. The characterization of the Fla2 system will help us to understand its role in the physiology of this microorganism.
30
Kanbe, M., S. Shibata, Y. Umino, U. Jenal e S. I. Aizawa. "Protease susceptibility of the Caulobacter crescentus flagellar hook–basal body: a possible mechanism of flagellar ejection during cell differentiation". Microbiology 151, n. 2 (1 febbraio 2005): 433–38. http://dx.doi.org/10.1099/mic.0.27386-0.
Testo completoAbstract (sommario):
When motile swarmer cells of Caulobacter crescentus differentiate into sessile stalked cells, the flagellum is ejected. To elucidate the molecular mechanism of the flagellar ejection, flagellar hook–basal body (HBB) complexes from C. crescentus were purified and characterized. The purified HBBs were less stable against acidic pH or protease treatment than HBBs of Salmonella typhimurium, supporting the view that flagellar ejection from C. crescentus is initiated by destruction of the fragile basal structures. In addition, protease treatment of the purified flagella resulted in the specific digestion of the MS ring complex, revealing for the first time the intact structure of the whole rod.
31
Murray, Thomas S., e Barbara I. Kazmierczak. "FlhF Is Required for Swimming and Swarming in Pseudomonas aeruginosa". Journal of Bacteriology 188, n. 19 (1 ottobre 2006): 6995–7004. http://dx.doi.org/10.1128/jb.00790-06.
Testo completoAbstract (sommario):
ABSTRACT FlhF is a signal recognition particle-like protein present in monotrichous bacteria. The loss of FlhF in various bacteria results in decreased transcription of class II, III, or IV flagellar genes, leads to diminished or absent motility, and results in the assembly of flagella at nonpolar locations on the cell surface. In this work, we demonstrate that the loss of FlhF results in defective swimming and swarming motility of Pseudomonas aeruginosa. The FlhF protein localizes to the flagellar pole; in the absence of FlhF, flagellar assembly occurs but is no longer restricted to the pole. ΔflhF bacteria swim at lower velocities than wild-type bacteria in liquid media and can no longer swarm when assayed under standard swarming conditions (0.5% agar). However, ΔflhF bacteria regain swarming behavior when plated on 0.3% agar. ΔflhF organisms show decreased transcription and expression of flagellin (FliC) both in liquid media and on swarming plates compared to wild-type bacteria. However, changes in flagellin expression do not explain the different motility patterns observed for ΔflhF bacteria. Instead, the aberrant placement of flagella in ΔflhF bacteria may reduce their ability to move this rod-shaped organism effectively.
32
González, Yael, Laura Camarena e Georges Dreyfus. "Induction of the lateral flagellar system of Vibrio shilonii is an early event after inhibition of the sodium ion flux in the polar flagellum". Canadian Journal of Microbiology 61, n. 3 (marzo 2015): 183–91. http://dx.doi.org/10.1139/cjm-2014-0579.
Testo completoAbstract (sommario):
In this study, we show the induction of lateral flagella by the action of the sodium channel blocker phenamil, in the marine bacterium Vibrio shilonii, a coral pathogen that causes bleaching. We analyzed the growth and morphology of cells treated with phenamil. A time course analysis showed that after 30 min of exposure to the sodium channel blocker, lateral flagella were present and could be detected by electron microscopy. Detection of the mRNA of the master regulator (lafK) and lateral flagellin (lafA) by RT–PCR confirmed the expression of lateral flagellar genes. We show the simultaneous isolation of polar and, for the first time, lateral flagellar hook-basal bodies. This allowed us to compare the dimensions and morphological characteristics of the 2 structures.
33
Inglis, Timothy J. J., Terry Robertson, Donald E. Woods, Nichole Dutton e Barbara J. Chang. "Flagellum-Mediated Adhesion by Burkholderia pseudomallei Precedes Invasion of Acanthamoeba astronyxis". Infection and Immunity 71, n. 4 (aprile 2003): 2280–82. http://dx.doi.org/10.1128/iai.71.4.2280-2282.2003.
Testo completoAbstract (sommario):
ABSTRACT In this study we investigated the role of the bacterial flagellum in Burkholderia pseudomallei entry to Acanthamoeba astronyxis trophozoites. B. pseudomallei cells were tethered to the external amoebic surface via their flagella. MM35, the flagellum-lacking fliC knockout derivative of B. pseudomallei NCTC 1026b did not demonstrate flagellum-mediated endocytosis in timed coculture, confirming that an intact flagellar apparatus assists B. pseudomallei entry into A. astronyxis.
34
Rementeria, A., A. B. Vivanco, A. Ramirez, F. L. Hernando, J. Bikandi, S. Herrera-León, A. Echeita e J. Garaizar. "Characterization of a Monoclonal Antibody Directed against Salmonella enterica Serovar Typhimurium and Serovar [4,5,12:i:−]". Applied and Environmental Microbiology 75, n. 5 (5 gennaio 2009): 1345–54. http://dx.doi.org/10.1128/aem.01597-08.
Testo completoAbstract (sommario):
ABSTRACT Flagellar extracts of Salmonella enterica serovars expressing phase 2 H1 antigenic complex (H:1,2, H:1,5, H:1,6, and H:1,7) and a mutant flagellin obtained by site-directed mutagenesis of the fljB gene from serovar Typhimurium at codon 218, transforming threonine to alanine, expressed in Escherichia coli (fljB218 A ) were used to analyze the H1 antigenic complex. Cross-reactions were detected by Western blotting and dot blotting using commercial polyclonal antibodies against the different wild-type extracts and mutant FljB218A. Therefore, we produced a monoclonal antibody (MAb), 23D4, isotyped as immunoglobulin M, against H:1,2 S. enterica serovar Typhimurium flagellin. The mutant flagellin was not recognized by this MAb. When a large number of phase 1 and phase 2 flagellin antigens of different serovars were used to characterize the 23D4 MAb, only extracts of serovars Typhimurium and [4,5,12:i:−] reacted. The protein composition of phase 1 and phase 2 extracts and highly purified H:1,2 flagellin from serovar Typhimurium strain LT2 and extract of strain 286 (serovar [4,5,12:i:−]), which reacted with the MAb, was studied. Phase 2 flagellin (FljBH:1,2) was detected in phase 1 and phase 2 flagellar heat extracts of serovar Typhimurium and was the single protein identified in all spots of purified H:1,2 flagellin. FliC, FlgK, and other proteins were detected in some immunoreactive spots and in the flagellar extract of serovar [4,5,12:i:−]. Immunoelectron microscopy of complete bacteria with 23D4 showed MAb attachment at the base of flagella, although the MAb failed to recognize the filament of flagella. Nevertheless, the results obtained by the other immunological tests (enzyme-linked immunosorbent assay, Western blotting, and dot blotting) indicate a reaction against flagellins. The epitopes could also be shared by other proteins on spots where FljB is not present, such as aminopeptidase B, isocitrate lyase, InvE, EF-TuA, enolase, DnaK, and others. In conclusion, MAb 23D4 can be useful for detection and diagnostic purposes of S. enterica serovar Typhimurium and serovar [4,5,12:i:−] and could be also helpful for epitope characterization of flagellum-associated antigens.
35
Tuson, Hannah H., Matthew F. Copeland, Sonia Carey, Ryan Sacotte e Douglas B. Weibel. "Flagellum Density Regulates Proteus mirabilis Swarmer Cell Motility in Viscous Environments". Journal of Bacteriology 195, n. 2 (9 novembre 2012): 368–77. http://dx.doi.org/10.1128/jb.01537-12.
Testo completoAbstract (sommario):
ABSTRACTProteus mirabilisis an opportunistic pathogen that is frequently associated with urinary tract infections. In the lab,P. mirabiliscells become long and multinucleate and increase their number of flagella as they colonize agar surfaces during swarming. Swarming has been implicated in pathogenesis; however, it is unclear how energetically costly changes inP. mirabiliscell morphology translate into an advantage for adapting to environmental changes. We investigated two morphological changes that occur during swarming—increases in cell length and flagellum density—and discovered that an increase in the surface density of flagella enabled cells to translate rapidly through fluids of increasing viscosity; in contrast, cell length had a small effect on motility. We found that swarm cells had a surface density of flagella that was ∼5 times larger than that of vegetative cells and were motile in fluids with a viscosity that inhibits vegetative cell motility. To test the relationship between flagellum density and velocity, we overexpressed FlhD4C2, the master regulator of the flagellar operon, in vegetative cells ofP. mirabilisand found that increased flagellum density produced an increase in cell velocity. Our results establish a relationship betweenP. mirabilisflagellum density and cell motility in viscous environments that may be relevant to its adaptation during the infection of mammalian urinary tracts and movement in contact with indwelling catheters.
36
Sal, Melanie S., Chunhao Li, M. A. Motalab, Satoshi Shibata, Shin-Ichi Aizawa e Nyles W. Charon. "Borrelia burgdorferi Uniquely Regulates Its Motility Genes and Has an Intricate Flagellar Hook-Basal Body Structure". Journal of Bacteriology 190, n. 6 (11 gennaio 2008): 1912–21. http://dx.doi.org/10.1128/jb.01421-07.
Testo completoAbstract (sommario):
ABSTRACT Borrelia burgdorferi is a flat-wave, motile spirochete that causes Lyme disease. Motility is provided by periplasmic flagella (PFs) located between the cell cylinder and an outer membrane sheath. The structure of these PFs, which are composed of a basal body, a hook, and a filament, is similar to the structure of flagella of other bacteria. To determine if hook formation influences flagellin gene transcription in B. burgdorferi, we inactivated the hook structural gene flgE by targeted mutagenesis. In many bacteria, completion of the hook structure serves as a checkpoint for transcriptional control of flagellum synthesis and other chemotaxis and motility genes. Specifically, the hook allows secretion of the anti-sigma factor FlgM and concomitant late gene transcription promoted by σ28. However, the control of B. burgdorferi PF synthesis differs from the control of flagellum synthesis in other bacteria; the gene encoding σ28 is not present in the genome of B. burgdorferi, nor are any σ28 promoter recognition sequences associated with the motility genes. We found that B. burgdorferi flgE mutants lacked PFs, were rod shaped, and were nonmotile, which substantiates previous evidence that PFs are involved in both cell morphology and motility. Although most motility and chemotaxis gene products accumulated at wild-type levels in the absence of FlgE, mutant cells had markedly decreased levels of the flagellar filament proteins FlaA and FlaB. Further analyses showed that the reduction in the levels of flagellin proteins in the spirochetes lacking FlgE was mediated at the posttranscriptional level. Taken together, our results indicate that in B. burgdorferi, the completion of the hook does not serve as a checkpoint for transcriptional regulation of flagellum synthesis. In addition, we also present evidence that the hook protein in B. burgdorferi forms a high-molecular-weight complex and that formation of this complex occurs in the periplasmic space.
37
Tomich, Mladen, Christine A. Herfst, Joseph W. Golden e Christian D. Mohr. "Role of Flagella in Host Cell Invasion by Burkholderia cepacia". Infection and Immunity 70, n. 4 (aprile 2002): 1799–806. http://dx.doi.org/10.1128/iai.70.4.1799-1806.2002.
Testo completoAbstract (sommario):
ABSTRACT Burkholderia cepacia is an important opportunistic human pathogen that affects immunocompromised individuals, particularly cystic fibrosis (CF) patients. Colonization of the lungs of a CF patient by B. cepacia can lead not only to a decline in respiratory function but also to an acute systemic infection, such as bacteremia. We have previously demonstrated that a CF clinical isolate of B. cepacia, strain J2315, can invade and survive within cultured respiratory epithelial cells. In order to further characterize the mechanisms of invasion of B. cepacia, we screened a transposon-generated mutant library of strain J2315 for mutants defective in invasion of A549 respiratory epithelial cells. Here we describe isolation and characterization of a nonmotile mutant of B. cepacia with reduced invasiveness due to disruption of fliG, which encodes a component of the motor-switch complex of the flagellar basal body. We also found that a defined null mutation in fliI, a gene encoding a highly conserved ATPase required for protein translocation via the flagellar type III secretion system, also resulted in loss of motility and a significant reduction in invasion. Both mutants lacked detectable intracellular flagellin and failed to export detectable amounts of flagellin into culture supernatants, suggesting that disruption of fliG and fliI impaired flagellar biogenesis. The reduction in invasion did not appear to be due to defective adherence of the flagellar mutants to A549 cells, suggesting that functional flagella and motility are required for full invasiveness of B. cepacia. Our findings indicate that flagellum-mediated motility may facilitate penetration of host epithelial barriers by B. cepacia, contributing to establishment of infection and systemic spread of the organism.
38
Tripepi, Manuela, Saheed Imam e Mechthild Pohlschröder. "Haloferax volcanii Flagella Are Required for Motility but Are Not Involved in PibD-Dependent Surface Adhesion". Journal of Bacteriology 192, n. 12 (2 aprile 2010): 3093–102. http://dx.doi.org/10.1128/jb.00133-10.
Testo completoAbstract (sommario):
ABSTRACT Although the genome of Haloferax volcanii contains genes (flgA1-flgA2) that encode flagellins and others that encode proteins involved in flagellar assembly, previous reports have concluded that H. volcanii is nonmotile. Contrary to these reports, we have now identified conditions under which H. volcanii is motile. Moreover, we have determined that an H. volcanii deletion mutant lacking flagellin genes is not motile. However, unlike flagella characterized in other prokaryotes, including other archaea, the H. volcanii flagella do not appear to play a significant role in surface adhesion. While flagella often play similar functional roles in bacteria and archaea, the processes involved in the biosynthesis of archaeal flagella do not resemble those involved in assembling bacterial flagella but, instead, are similar to those involved in producing bacterial type IV pili. Consistent with this observation, we have determined that, in addition to disrupting preflagellin processing, deleting pibD, which encodes the preflagellin peptidase, prevents the maturation of other H. volcanii type IV pilin-like proteins. Moreover, in addition to abolishing swimming motility, and unlike the flgA1-flgA2 deletion, deleting pibD eliminates the ability of H. volcanii to adhere to a glass surface, indicating that a nonflagellar type IV pilus-like structure plays a critical role in H. volcanii surface adhesion.
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Murat, Dorothée, Marion Hérisse, Leon Espinosa, Alicia Bossa, François Alberto e Long-Fei Wu. "Opposite and Coordinated Rotation of Amphitrichous Flagella Governs Oriented Swimming and Reversals in a Magnetotactic Spirillum". Journal of Bacteriology 197, n. 20 (3 agosto 2015): 3275–82. http://dx.doi.org/10.1128/jb.00172-15.
Testo completoAbstract (sommario):
ABSTRACTCurrent knowledge regarding the mechanism that governs flagellar motor rotation in response to environmental stimuli stems mainly from the study of monotrichous and peritrichous bacteria. Little is known about how two polar flagella, one at each cell pole of the so-called amphitrichous bacterium, are coordinated to steer the swimming. Here we fluorescently labeled the flagella ofMagnetospirillum magneticumAMB-1 cells and took advantage of the magnetically controllable swimming of this bacterium to investigate flagellar rotation in moving cells. We identified three motility behaviors (runs, tumbles, and reversals) and two characteristic fluorescence patterns likely corresponding to flagella rotating in opposite directions. Each AMB-1 locomotion mode was systematically associated with particular flagellar patterns at the poles which led us to conclude that, while cell runs are allowed by the asymmetrical rotation of flagellar motors, their symmetrical rotation triggers cell tumbling. Our observations point toward a precise coordination of the two flagellar motors which can be temporarily unsynchronized during tumbling.IMPORTANCEMotility is essential for bacteria to search for optimal niches and survive. Many bacteria use one or several flagella to explore their environment. The mechanism by which bipolarly flagellated cells coordinate flagellar rotation is poorly understood. We took advantage of the genetic amenability and magnetically controlled swimming of the spirillum-shaped magnetotactic bacteriumMagnetospirillum magneticumAMB-1 to correlate cell motion with flagellar rotation. We found that asymmetric rotation of the flagella (counterclockwise at the lagging pole and clockwise at the leading pole) enables cell runs whereas symmetric rotation triggers cell tumbling. Taking into consideration similar observations in spirochetes, bacteria possessing bipolar ribbons of periplasmic flagella, we propose a conserved motility paradigm for spirillum-shaped bipolarly flagellated bacteria.
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Shelswell, Kristopher J., Terumi A. Taylor e J. Thomas Beatty. "Photoresponsive Flagellum-Independent Motility of the Purple Phototrophic Bacterium Rhodobacter capsulatus". Journal of Bacteriology 187, n. 14 (luglio 2005): 5040–43. http://dx.doi.org/10.1128/jb.187.14.5040-5043.2005.
Testo completoAbstract (sommario):
ABSTRACT We report the discovery of photoresponsive, flagellum-independent motility of the α-proteobacterium Rhodobacter capsulatus, a nonsulfur purple phototrophic bacterium. This motility takes place in the 1.5% agar-glass interface of petri plates but not in soft agar, and cells move toward a light source. The appearances of motility assay plates inoculated with wild-type or flagellum-deficient mutants indicate differential contributions from flagellar and flagellum-independent mechanisms. Electron microscopy confirmed the absence of flagella in flagellar mutants and revealed the presence of pilus-like structures at one pole of wild-type and mutant cells. We suggest that R. capsulatus utilizes a flagellum-independent, photoresponsive mechanism that resembles twitching motility to move in a line away from the point of inoculation toward a light source.
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Grünenfelder, Björn, Stefanie Gehrig e Urs Jenal. "Role of the Cytoplasmic C Terminus of the FliF Motor Protein in Flagellar Assembly and Rotation". Journal of Bacteriology 185, n. 5 (1 marzo 2003): 1624–33. http://dx.doi.org/10.1128/jb.185.5.1624-1633.2003.
Testo completoAbstract (sommario):
ABSTRACT Twenty-six FliF monomers assemble into the MS ring, a central motor component of the bacterial flagellum that anchors the structure in the inner membrane. Approximately 100 amino acids at the C terminus of FliF are exposed to the cytoplasm and, through the interaction with the FliG switch protein, a component of the flagellar C ring, are essential for the assembly of the motor. In this study, we have dissected the entire cytoplasmic C terminus of the Caulobacter crescentus FliF protein by high-resolution mutational analysis and studied the mutant forms with regard to the assembly, checkpoint control, and function of the flagellum. Only nine amino acids at the very C terminus of FliF are essential for flagellar assembly. Deletion or substitution of about 10 amino acids preceding the very C terminus of FliF resulted in assembly-competent but nonfunctional flagella, making these the first fliF mutations described so far with a Fla+ but Mot− phenotype. Removal of about 20 amino acids further upstream resulted in functional flagella, but cells carrying these mutations were not able to spread efficiently on semisolid agar plates. At least 61 amino acids located between the functionally relevant C terminus and the second membrane-spanning domain of FliF were not required for flagellar assembly and performance. A strict correlation was found between the ability of FliF mutant versions to assemble into a flagellum, flagellar class III gene expression, and a block in cell division. Motile suppressors could be isolated for nonmotile mutants but not for mutants lacking a flagellum. Several of these suppressor mutations were localized to the 5′ region of the fliG gene. These results provide genetic support for a model in which only a short stretch of amino acids at the immediate C terminus of FliF is required for flagellar assembly through stable interaction with the FliG switch protein.
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Nohýnková, Eva, Pavla Tůmová e Jaroslav Kulda. "Cell Division of Giardia intestinalis: Flagellar Developmental Cycle Involves Transformation and Exchange of Flagella between Mastigonts of a Diplomonad Cell". Eukaryotic Cell 5, n. 4 (aprile 2006): 753–61. http://dx.doi.org/10.1128/ec.5.4.753-761.2006.
Testo completoAbstract (sommario):
ABSTRACT Giardia intestinalis is a binucleated diplomonad possessing four pairs of flagella of distinct location and function. Its pathogenic potential depends on the integrity of a complex microtubular cytoskeleton that undergoes a profound but poorly understood reorganization during cell division. We examined the cell division of G. intestinalis with the aid of light and electron microscopy and immunofluorescence methods and present here new observations on the reorganization of the flagellar apparatus in the dividing Giardia. Our results demonstrated the presence of a flagellar maturation process during which the flagella migrate, assume different position, and transform to different flagellar types in progeny until their maturation is completed. For each newly assembled flagellum it takes three cell cycles to become mature. The mature flagellum of Giardia is the caudal one that possesses a privileged basal body at which the microtubules of the adhesive disk nucleate. In contrast to generally accepted assumption that each of the two diplomonad mastigonts develops separately, we found that they are developmentally linked, exchanging their cytoskeletal components at the early phase of mitosis. The presence of the flagellar maturation process in a metamonad protist Giardia suggests that the basal body or centriole maturation is a universal phenomenon that may represent one of the core processes in a eukaryotic cell.
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Sampaio, Suely C. F., Wilson B. Luiz, Mônica A. M. Vieira, Rita C. C. Ferreira, Bruna G. Garcia, Rita Sinigaglia-Coimbra, Jorge L. M. Sampaio, Luís C. S. Ferreira e Tânia A. T. Gomes. "Flagellar Cap Protein FliD Mediates Adherence of Atypical Enteropathogenic Escherichia coli to Enterocyte Microvilli". Infection and Immunity 84, n. 4 (1 febbraio 2016): 1112–22. http://dx.doi.org/10.1128/iai.01001-15.
Testo completoAbstract (sommario):
The expression of flagella correlates with different aspects of bacterial pathogenicity, ranging from adherence to host cells to activation of inflammatory responses by the innate immune system. In the present study, we investigated the role of flagella in the adherence of an atypical enteropathogenicEscherichia coli(aEPEC) strain (serotype O51:H40) to human enterocytes. Accordingly, isogenic mutants deficient in flagellin (FliC), the flagellar structural subunit; the flagellar cap protein (FliD); or the MotAB proteins, involved in the control of flagellar motion, were generated and tested for binding to differentiated Caco-2 cells. Binding of the aEPEC strain to enterocytes was significantly impaired in strains with thefliCandfliDgenes deleted, both of which could not form flagella on the bacterial surface. A nonmotile but flagellated MotAB mutant also showed impaired adhesion to Caco-2 cells. In accordance with these observations, adhesion of aEPEC strain 1711-4 to Caco-2 cells was drastically reduced after the treatment of Caco-2 cells with purified FliD. In addition, incubation of aEPEC bacteria with specific anti-FliD serum impaired binding to Caco-2 cells. Finally, incubation of Caco-2 cells with purified FliD, followed by immunolabeling, showed that the protein was specifically bound to the microvillus tips of differentiated Caco-2 cells. The aEPEC FliD or anti-FliD serum also reduced the adherence of prototype typical enteropathogenic, enterohemorrhagic, and enterotoxigenicE. colistrains to Caco-2 cells. In conclusion, our findings further strengthened the role of flagella in the adherence of aEPEC to human enterocytes and disclosed the relevant structural and functional involvement of FliD in the adhesion process.
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Boesger, Jens, Volker Wagner, Wolfram Weisheit e Maria Mittag. "Analysis of Flagellar Phosphoproteins from Chlamydomonas reinhardtii". Eukaryotic Cell 8, n. 7 (8 maggio 2009): 922–32. http://dx.doi.org/10.1128/ec.00067-09.
Testo completoAbstract (sommario):
ABSTRACT Cilia and flagella are cell organelles that are highly conserved throughout evolution. For many years, the green biflagellate alga Chlamydomonas reinhardtii has served as a model for examination of the structure and function of its flagella, which are similar to certain mammalian cilia. Proteome analysis revealed the presence of several kinases and protein phosphatases in these organelles. Reversible protein phosphorylation can control ciliary beating, motility, signaling, length, and assembly. Despite the importance of this posttranslational modification, the identities of many ciliary phosphoproteins and knowledge about their in vivo phosphorylation sites are still missing. Here we used immobilized metal affinity chromatography to enrich phosphopeptides from purified flagella and analyzed them by mass spectrometry. One hundred forty-one phosphorylated peptides were identified, belonging to 32 flagellar proteins. Thereby, 126 in vivo phosphorylation sites were determined. The flagellar phosphoproteome includes different structural and motor proteins, kinases, proteins with protein interaction domains, and many proteins whose functions are still unknown. In several cases, a dynamic phosphorylation pattern and clustering of phosphorylation sites were found, indicating a complex physiological status and specific control by reversible protein phosphorylation in the flagellum.
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Stafford, Graham P., Tomoo Ogi e Colin Hughes. "Binding and transcriptional activation of non-flagellar genes by the Escherichia coli flagellar master regulator FlhD2C2". Microbiology 151, n. 6 (1 giugno 2005): 1779–88. http://dx.doi.org/10.1099/mic.0.27879-0.
Testo completoAbstract (sommario):
The gene hierarchy directing biogenesis of peritrichous flagella on the surface of Escherichia coli and other enterobacteria is controlled by the heterotetrameric master transcriptional regulator FlhD2C2. To assess the extent to which FlhD2C2 directly activates promoters of a wider regulon, a computational screen of the E. coli genome was used to search for gene-proximal DNA sequences similar to the 42–44 bp inverted repeat FlhD2C2 binding consensus. This identified the binding sequences upstream of all eight flagella class II operons, and also putative novel FlhD2C2 binding sites in the promoter regions of 39 non-flagellar genes. Nine representative non-flagellar promoter regions were all bound in vitro by active reconstituted FlhD2C2 over the K D range 38–356 nM, and of the nine corresponding chromosomal promoter–lacZ fusions, those of the four genes b1904, b2446, wzz fepE and gltI showed up to 50-fold dependence on FlhD2C2 in vivo. In comparison, four representative flagella class II promoters bound FlhD2C2 in the K D range 12–43 nM and were upregulated in vivo 30- to 990-fold. The FlhD2C2-binding sites of the four regulated non-flagellar genes overlap by 1 or 2 bp the predicted −35 motif of the FlhD2C2-activated σ 70 promoters, as is the case with FlhD2C2-dependent class II flagellar promoters. The data indicate a wider FlhD2C2 regulon, in which non-flagellar genes are bound and activated directly, albeit less strongly, by the same mechanism as that regulating the flagella gene hierarchy.
46
Jagannathan, Aparna, Chrystala Constantinidou e Charles W. Penn. "Roles of rpoN, fliA,and flgR in Expression of Flagella inCampylobacter jejuni". Journal of Bacteriology 183, n. 9 (1 maggio 2001): 2937–42. http://dx.doi.org/10.1128/jb.183.9.2937-2942.2001.
Testo completoAbstract (sommario):
ABSTRACT Three potential regulators of flagellar expression present in the genome sequence of Campylobacter jejuni NCTC 11168, the genes rpoN, flgR, andfliA, which encode the alternative sigma factor ς54, the ς54-associated transcriptional activator FlgR, and the flagellar sigma factor ς28, respectively, were investigated for their role in global regulation of flagellar expression. The three genes were insertionally inactivated inC. jejuni strains NCTC 11168 and NCTC 11828. Electron microscopic studies of the wild-type and mutant strains showed that therpoN and flgR mutants were nonflagellate and that the fliA mutant had truncated flagella. Immunoblotting experiments with the three mutants confirmed the roles of rpoN, flgR, and fliA in the expression of flagellin.
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Ciacci-Woolwine, Federica, Patrick F. McDermott e Steven B. Mizel. "Induction of Cytokine Synthesis by Flagella from Gram-Negative Bacteria May Be Dependent on the Activation or Differentiation State of Human Monocytes". Infection and Immunity 67, n. 10 (1 ottobre 1999): 5176–85. http://dx.doi.org/10.1128/iai.67.10.5176-5185.1999.
Testo completoAbstract (sommario):
ABSTRACT We have previously demonstrated that salmonellae, but notEscherichia coli or Yersinia enterocolitica, stimulates tumor necrosis factor alpha (TNFα) production in the human promonocytic cell line U38. Subsequent analysis revealed that the TNFα-inducing activity of salmonellae was associated with flagellin, a major component of flagella from gram-negative bacteria. In the present study, we have explored the basis for the apparent specificity of action of Salmonella flagella on TNFα expression in U38 cells and have extended this analysis to normal human peripheral blood mononuclear cells (PBMC). Flagella from the enteropathogenicE. coli strain E2348/69, Y. enterocoliticaJB580, and Pseudomonas aeruginosa PAO1, which did not induce significant levels of TNFα production in U38 cells, were as potent as Salmonella flagella in terms of TNFα and interleukin 1β activation in PBMC. However, TNFα production in U38 cells was greatly enhanced when these cells were stimulated with flagella from E. coli, Y. enterocolitica, andP. aeruginosa in the presence of a costimulant, phorbol 13-myristate acetate. These findings are consistent with the hypothesis that the activation or differentiation state of a monocyte may have a substantial effect on the cell’s responsiveness to flagellum stimulation of cytokine synthesis. Furthermore, these results indicate that cytokine induction in monocytes may be a general property of flagella from gram-negative bacteria.
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Martinez, Raquel M., Madushini N. Dharmasena, Thomas J. Kirn e Ronald K. Taylor. "Characterization of Two Outer Membrane Proteins, FlgO and FlgP, That Influence Vibrio cholerae Motility". Journal of Bacteriology 191, n. 18 (10 luglio 2009): 5669–79. http://dx.doi.org/10.1128/jb.00632-09.
Testo completoAbstract (sommario):
ABSTRACT Vibrio cholerae is highly motile by the action of a single polar flagellum. The loss of motility reduces the infectivity of V. cholerae, demonstrating that motility is an important virulence factor. FlrC is the sigma-54-dependent positive regulator of flagellar genes. Recently, the genes VC2206 (flgP) and VC2207 (flgO) were identified as being regulated by FlrC via a microarray analysis of an flrC mutant (D. C. Morris, F. Peng, J. R. Barker, and K. E. Klose, J. Bacteriol. 190:231-239, 2008). FlgP is reported to be an outer membrane lipoprotein required for motility that functions as a colonization factor. The study reported here focuses on the characterization of flgO, the first gene in the flgOP operon. We show that FlgO and FlgP are important for motility, as strains with mutations in the flgOP genes have reduced motility phenotypes. The flgO and flgP mutant populations display fewer motile cells as well as reduced numbers of flagellated cells. The flagella produced by the flgO and flgP mutant strains are shorter in length than the wild-type flagella, which can be restored by inhibiting rotation of the flagellum. FlgO is an outer membrane protein that localizes throughout the membrane and not at the flagellar pole. Although FlgO and FlgP do not specifically localize to the flagellum, they are required for flagellar stability. Due to the nature of these motility defects, we established that the flagellum is not sufficient for adherence; rather, motility is the essential factor required for attachment and thus colonization by V. cholerae O1 of the classical biotype. This study reveals a novel mechanism for which the outer membrane proteins FlgO and FlgP function in motility to mediate flagellar stability and influence attachment and colonization.
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Haya, Shohei, Yuya Tokumaru, Naoki Abe, Jun Kaneko e Shin-ichi Aizawa. "Characterization of Lateral Flagella of Selenomonas ruminantium". Applied and Environmental Microbiology 77, n. 8 (18 febbraio 2011): 2799–802. http://dx.doi.org/10.1128/aem.00286-11.
Testo completoAbstract (sommario):
ABSTRACTSelenomonas ruminantiumproduces a tuft of flagella near the midpoint of the cell body and swims by rotating the cell body along the cell's long axis. The flagellum is composed of a single kind of flagellin, which is heavily glycosylated. The hook length ofS. ruminantiumis almost double that ofSalmonella.
50
Albert-Weissenberger, Christiane, Tobias Sahr, Odile Sismeiro, Jörg Hacker, Klaus Heuner e Carmen Buchrieser. "Control of Flagellar Gene Regulation in Legionella pneumophila and Its Relation to Growth Phase". Journal of Bacteriology 192, n. 2 (13 novembre 2009): 446–55. http://dx.doi.org/10.1128/jb.00610-09.
Testo completoAbstract (sommario):
ABSTRACT The bacterial pathogen Legionella pneumophila responds to environmental changes by differentiation. At least two forms are well described: replicative bacteria are avirulent; in contrast, transmissive bacteria express virulence traits and flagella. Phenotypic analysis, Western blotting, and electron microscopy of mutants of the regulatory genes encoding RpoN, FleQ, FleR, and FliA demonstrated that flagellin expression is strongly repressed and that the mutants are nonflagellated in the transmissive phase. Transcriptome analyses elucidated that RpoN, together with FleQ, enhances transcription of 14 out of 31 flagellar class II genes, which code for the basal body, hook, and regulatory proteins. Unexpectedly, FleQ independent of RpoN enhances the transcription of fliA encoding sigma 28. Expression analysis of a fliA mutant showed that FliA activates three out of the five remaining flagellar class III genes and the flagellar class IV genes. Surprisingly, FleR does not induce but inhibits expression of at least 14 flagellar class III genes on the transcriptional level. Thus, we propose that flagellar class II genes are controlled by FleQ and RpoN, whereas the transcription of the class III gene fliA is controlled in a FleQ-dependent but RpoN-independent manner. However, RpoN and FleR might influence flagellin synthesis on a posttranscriptional level. In contrast to the commonly accepted view that enhancer-binding proteins such as FleQ always interact with RpoN to fullfill their regulatory functions, our results strongly indicate that FleQ regulates gene expression that is RpoN dependent and RpoN independent. Finally, FliA induces expression of flagellar class III and IV genes leading to the complete synthesis of the flagellum.