Morphological distinction between different H serotypes of Escherichia coli.

The structure of the flagellar filaments of 50 Escherichia coli strains, each with a different H antigen, was examined. Although the flagella within each strain were structurally identical, there was variability in flagellar surface pattern between strains with differrent H antigens. Investigation of additional strains confirmed that flagella structure was the same in all strains having the same H antigen. In three pairs of strains with cross-reacting H antigens, the antigenic relatedness was associated with identical flagella structure.     

Attachment and structural features of flagella of certain bacilli

Abram, Dinah (Purdue University, Lafayette, Ind.), A. E. Vatter, and Henry Koffler. Attachment and structural features of flagella of certain bacilli. J. Bacteriol. 91:2045-2068. 1966.-The attachment of flagella to cells of various mesophilic and thermophilic strains of Bacillus was studied electron microscopically. Studies of ghost cells and membrane fragments indicate that flagella are connected to the cytoplasmic membrane. Flagella removed from cells mechanically, during autolysis, or by phage lysis, have attached to the base of their proximal hooks material that is heterogeneous in character. In part, this material consists of cytoplasmic membrane; its varied shape appears to be caused by the folding of the membrane around the proximal end of the flagellum at the site of attachment. It is uncertain whether this material represents a real structure or an artifact. Highresolution microscopy reveals differences in the fine structure of intact flagella of the various strains studied. The proximal hook and the flagellar filament are distinct in morphology and fine structure. A specialized structure is associated with the hook of flagella of B. brevis and B. circulans. The filament of flagella of B. stearothermophilus 2184 has two regions that show marked differences in the manner in which the subunits appear to be organized. No correlation was found between the site of origin of flagella and the location of reduced tellurite when the reduction of potassium tellurite was used to indicate the loci of enzymatic respiratory activities.     

Comparison of the flagellins from different flagellar morphotypes of Escherichia coli.

The molecular weights of the flagellins of 13 strains of Escherichia coli, each with a different H antigen, were estimated using polyacrylamide gel electrophoresis. In each case only one major polypeptide was demonstrated, although some strains possessed apparently sheathed flagella. Considerable differences in the molecular weight of flagellin accompanied the previously described structural differences between flagella from strains with different H antigens. The relationship between flagellar diameter and the molecular weight of the corresponding flagellins was similar for both unsheathed and apparently sheathed flagella. Crosss-polymerization occurred between seed consisting of fragment of unsheathed flagella and flagellin solution from apparently sheathed flagella and vice versa. Co-polymerization of flagellin from unsheathed flagella and flagellin from apparently sheathed flagella was also demonstrated. These polymerization experiments indicate that the assembly pattern of flagellin molecules is probably the same in all E. coli flagella. The above and other evidence suggests that there is no true sheath, but that the differences in flagellar surface structure between different E. coli flagella are the result of differences in the superficial parts of the flagellin molecules.     

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.     

Formation of flagella during interphase in secondary spermatocytes from Xenopus laevis in vitro

In cell culture, single motile flagella, 1 micron in length, were observed to grow from secondary spermatocytes of Xenopus laevis within 2-3 hours after telophase I, at 22 degrees C. About 90% of the secondary spermatocytes formed flagella as observed by phase-contrast microscopy. The flagella grew up to 2-6 microns in length during interphase II, which lasted about 18 hours. The presence of the "9 + 2" microtubular structure of the flagellar axonemes of secondary spermatocytes was confirmed by electron microscopy. When chromosomal condensation began (prophase II), the flagella were resorbed into the cells and, after the second meiotic division, a flagellum was formed again by each of the round spermatids. Thus, there appears to be a close relationship between the meiotic division cycle and the formation of flagella. The possible contribution of Sertoli cells to the formation of flagella in secondary spermatocytes was examined by reducing the number of Sertoli cells to less than ten per culture. Under these conditions, flagella formed in secondary spermatocytes with very high efficiency. It is very likely that secondary spermatocytes form flagella in vivo, since the secondary spermatocytes were observed to have flagella immediately after dissociation of the testes.     

Electron microscopy of bundled flagella of the curly mutant of Salmonella abortivoequina

Mitani, Michiko (National Institute of Genetics, Mishima, Japan), and Tetsuo Iino. Electron microscopy of bundled flagella of the curly mutant of Salmonella abortivoequina. J. Bacteriol. 90:1096-1101. 1965.-The arrangement of flagella was observed by dark-field and electron microscopy in three strains of Salmonella abortivoequina, namely, normal flagellar, curly flagellar, and paralyzed curly flagellar strains. With dark-field microscopy, bundled flagella could be seen in 5 to 10% of actively moving normal or curly mutant cells. Under the electron microscope, a great many bundled flagella were observed in the curly mutant strain, but in the normal strain most of the flagella were dissociated or the bundles were rather loose and irregular. Normal flagella seem to separate easily during the process of preparation, but not the curly ones. Single flagella were found to run parallel with each other and to form a bundle consisting of five or more flagella; the bundle was spirally gyrating, with the characteristic flagellar wave. It is thought that the bundle observed with the electron microscope corresponds to that observed under the dark-field microscope. Further, the marked decrease of bundle formation in the paralyzed curly mutant cells suggests that bundle formation is not caused by curly flagellar structure per se, but corresponds to the mode of locomotion of peritrichously flagellated bacteria.     

"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.     

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.     

Structure and Arrangement of Flagella in Species of the Genus Beneckea and Photobacterium fischeri

Species of marine bacteria belonging to the genus Beneckea and strains of Photobacterium fischeri were negatively stained and examined by means of the electron microscope to determine the structure and arrangement of their flagella. All of the species of the genus Beneckea had single, polar, sheathed flagella when grown in liquid medium. When grown on solid medium, most strains of B. campbellii and B. neptuna and all strains of B. alginolytica and B. parahaemolytica had unsheathed, peritrichous flagella in addition to the single, sheathed, polar flagellum. The remaining species, B. nereida, B. pelagia, and B. natriegens, had a single, polar, sheathed flagellum when grown on solid medium. Strains of P. fischeri had sheathed flagella arranged in polar tufts. Only one group (B-2) of marine bacteria included in this study was found to have polar, unsheathed flagella.     

Basal structure and attachment of flagella in cells of Proteus vulgaris

Abram, Dinah (Purdue University, Lafayette, Ind.), Henry Koffler, and A. E. Vatter. Basal structure and attachment of flagella in cells of Proteus vulgaris. J. Bacteriol. 90:1337-1354. 1965.-The attachment of flagella to cells of Proteus vulgaris was studied electron microscopically with negatively stained and shadow-cast preparations of ghosts from standard cultures and from special cultures that produced "long forms." The flagellum, the basal portion of which is hooked, arises within the cell from a nearly spherical structure, 110 to 140 A in diameter. This structure appears to be associated with the cytoplasmic membrane; it may be a part of the membrane or a separate entity that lies just beneath the membrane. Flagella associated with cell walls free from cytoplasmic membrane frequently have larger bodies, 200 to 700 A in diameter, associated with their base. These structures probably consist at least partly of fragments of the cytoplasmic membrane, a portion of which folds around a smaller structure. Flagella in various stages of development were observed in long forms of P. vulgaris cells grown at low temperature. The basal structure of these flagella was similar to that of the long or "mature" flagella. Strands connecting the basal structures were observed in ghosts of long forms; these strands appear to be derived from the cytoplasmic membrane. Flagella were found to be attached to fragments of cell wall and to cytoplasmic membrane in a similar manner as they are attached to ghosts. In isolates of flagella that have been separated from the cells mechanically, the organelles often terminate in hooks which almost always appear naked, but have a different fine structure than the flagellum proper.     

Actin in mating structures of Chlamydomonas eugametos gametes

The presence of actin in Chlamydomonas eugametos mating structures was studied using monoclonal anti-actin antibodies. Immunofluorescent labelling of mating gametes clearly stained their mating structures and this was confirmed at the electron microscope level by immunogold labelling of sections. Anti-actin labelling also strongly stained the flagella at the flagellar collar regions and weakly stained the rest of the flagella. Treatment of gametes with 6–8% ethanol induced mating structures which protruded as large 'balloons'. Balloons stained brilliantly with anti-actin antibodies and weakly with FITC-phalloidin, a fluorescent reagent that stains F-actin. Isolated mating structure balloons and flagella were analyzed using western blotting. A prominent 43 kDa band, co-migrating with actin in erythrocyte ghosts, reacted with anti-actin antibodies. The results indicate that actin is present in mating structures and flagella of both mating types of C, eugametos .     

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.     

Effect of Flagellar Mutations on Yersinia enterocolitica Biofilm Formation

Yersinia enterocolitica biovar 1B is one of a number of strains pathogenic to humans in the genus Yersinia. It has three different type III secretion systems, Ysc, Ysa, and the flagella. In this study, the effect of flagella on biofilm formation was evaluated. In a panel of 31 mutant Y. enterocolitica strains, we observed that mutations that abolish the structure or rotation of the flagella greatly reduce biofilm formation when the bacteria are grown under static conditions. These results were further evaluated by assessing biofilm formation under continuous culture using a flow cell chamber. The results confirmed the important contribution of flagella to the initiation of biofilm production but indicated that there are differences in the progression of biofilm development between static growth and flow conditions. Our results suggest that flagella play a critical role in biofilm formation in Y. enterocolitica.     

Unfolding of tertiary structure ofHalobacterium halobium flagellins does not result in flagella destruction

The structure ofHalobacterium halobium R₁M₁ flagella is investigated by the methods of scanning microcalorimetry, circular dichroism, and electron microscopy. It is shown that melting curves of flagella in solutions with a different concentration of NaCl display only one peak of heat capacity that corresponds to one cooperatively melting domain. It is found that flagella do not dissociate after melting. The possible structural organization of archaebacterial flagella is discussed.     

Unfolding of tertiary structure ofHalobacterium halobium flagellins does not result in flagella destruction

The structure ofHalobacterium halobium R₁M₁ flagella is investigated by the methods of scanning microcalorimetry, circular dichroism, and electron microscopy. It is shown that melting curves of flagella in solutions with a different concentration of NaCl display only one peak of heat capacity that corresponds to one cooperatively melting domain. It is found that flagella do not dissociate after melting. The possible structural organization of archaebacterial flagella is discussed.     

Flagellar protein dynamics in Chlamydomonas

Cilia and flagella appear to be stable, terminal, microtubule-containing organelles, but they also elongate and shorten in response to a variety of signals. To understand mechanisms that regulate flagellar dynamics, Chlamydomonas cells with nongrowing flagella were labeled with (35)S, and flagella and basal body components were examined for labeled polypeptides. Maximal incorporation of label into the flagella occurred within 3 h. Twenty percent of the flagellar polypeptides were exchanged. These included tubulins, dyneins, and 80 other axonemal and membrane plus matrix polypeptides. The most stable flagellar structure is the PF-ribbon, which comprises part of the wall of each doublet microtubule and is composed of tubulin and three other polypeptides. Most (35)S was incorporated into the high molecular weight ribbon polypeptide, rib240, and little, if any, (35)S is incorporated into PF-ribbon-associated tubulin. Both wild-type (9 + 2) and 9 + 0 flagella, which lack central microtubules, exhibited nearly identical exchange patterns, so labeling is not due to turnover of relatively labile central microtubules. To determine if flagellar length is balanced by protein exchange, (35)S incorporation into disassembling flagella was examined, as was exchange in flagella in which microtubule assembly was blocked by colchicine. Incorporation of (35)S-labeled polypeptides was found to occur into flagellar axonemes during wavelength-dependent shortening in pf18 and in fla10 cells induced to shorten flagella by incubation at 33 degrees C. Colchicine blocked tubulin addition but did not affect the exchange of the other exchangeable polypeptides; nor did it induce any change in flagellar length. Basal bodies also incorporated newly synthesized proteins. These data reveal that Chlamydomonas flagella are dynamic structures that incorporate new protein both during steady state and as flagella shorten and that protein exchange does not, alone, explain length regulation.     

Purification and Thermal Stability of Intact Bacillus subtilis Flagella

Flagella were prepared and purified in a relatively intact form from bacterial lysates. Immunochemical tests showed that over 95% of the protein in the final preparation consisted of flagellar antigen. These flagella are more stable to thermal denaturation than flagella filaments obtained by shearing. Their thermal properties more closely resemble those of flagella in the native state on bacteria. The presence of the hook structure is responsible for this extra stability.     

Bend propagation drives central pair rotation in Chlamydomonas reinhardtii flagella

Regulation of motile 9+2 cilia and flagella depends on interactions between radial spokes and a central pair apparatus. Although the central pair rotates during bend propagation in flagella of many organisms and rotation correlates with a twisted central pair structure, propulsive forces for central pair rotation and twist are unknown. Here we compared central pair conformation in straight, quiescent flagella to that in actively beating flagella using wild-type Chlamydomonas reinhardtii and mutants that lack radial spoke heads. Twists occur in quiescent flagella in both the presence and absence of spoke heads, indicating that spoke--central pair interactions are not needed to generate torque for twisting. Central pair orientation in propagating bends was also similar in wild type and spoke head mutant strains, thus orientation is a passive response to bend formation. These results indicate that bend propagation drives central pair rotation and suggest that dynein regulation by central pair--radial spoke interactions involves passive central pair reorientation to changes in bend plane.     

Flagella and Pili of Iron-Oxidizing Thiobacilli Isolated from a Uranium Mine in Northern Ontario, Canada

Five strains of Thiobacillus ferrooxidans, which included three recent isolates from a uranium mine, possessed flagella. Three of the strains had several pili per cell. The dimensions, fine structure, and orientation of the flagella were different. Both polar and peritrichous flagella were observed, indicating strain-dependent ultrastructural variation in acidophilic thiobacilli. Neither flagella nor pili were detected in eight other strains of T. ferrooxidans and two strains of Thiobacillus acidophilus by electron microscopy, although all of the cultures contained motile cells.