The bacterial linear motor of <i>Spiroplasma melliferum</i> BC3: from single molecules to swimming cells

Trachtenberg, Shlomo; Gilad, Rami; Geffen, Nima

doi:10.1046/j.1365-2958.2003.t01-1-03200.x

Cited by 36 publications

(46 citation statements)

References 29 publications

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“…Because the fibril length depends on subunit axial length, the range of axial lengths is expected to correlate with the range of fibril lengths at all conformational states. We find that this is indeed the case (22), which is reflected in the results and data analysis below. Images of single and paired fibrils.…”

Section: Resultssupporting

confidence: 48%

“…Thus, the frequency of subunit size distribution may differ between the in vivo and in vitro states, even though the range of subunit axial lengths does not. This would explain the relatively sharp (22). The number of subunits per fibril unit length is constant, ϳ100 fully expanded subunits per micrometer.…”

Section: Resultsmentioning

confidence: 98%

“…To this point, data analysis has been based on diffraction patterns of images of ribbons and bundles in which all structural features are averaged, but the cytoskeletal ribbons are linear motors whose subunit spacing is expected to vary during contraction and expansion (21,22). Whereas the average distances between subunits are determined by the spatial frequencies of the diffraction spots, the variation in subunit spacing can be determined directly from images.…”

Section: Resultsmentioning

confidence: 99%

“…This is where the analogy with the Spiroplasma cytoskeleton ends; Spiroplasma fibrils are extremely stable and resistant to depolymerization, unlike MreB ribbons. Moreover, a clear range of (differential) axial length changes, correlating with the dynamic, helical geometry of the cell, has been observed for Spiroplasma fibrils and in the molecules along their length, suggesting contractility (22).…”

Section: Vol 185 2003mentioning

confidence: 99%

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Mass Distribution and Spatial Organization of the Linear Bacterial Motor ofSpiroplasma citriR8A2

2003

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In the simple, helical, wall-less bacterial genus Spiroplasma, chemotaxis and motility are effected by a linear, contractile motor arranged as a flat cytoskeletal ribbon attached to the inner side of the membrane along the shortest helical line. With scanning transmission electron microscopy and diffraction analysis, we determined the hierarchical and spatial organization of the cytoskeleton of Spiroplasma citri R8A2. The structural unit appears to be a fibril, ϳ5 nm wide, composed of dimers of a 59-kDa protein; each ribbon is assembled from seven fibril pairs. The functional unit of the intact ribbon is a pair of aligned fibrils, along which pairs of dimers form tetrameric ring-like repeats. On average, isolated and purified ribbons contain 14 fibrils or seven well-aligned fibril pairs, which are the same structures observed in the intact cell. Scanning transmission electron microscopy mass analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified cytoskeletons indicate that the 59-kDa protein is the only constituent of the ribbons.The mollicutes (Spiroplasma, Mycoplasma, and Acholeplasma spp.) are the smallest and simplest free-living and selfreplicating forms of life. The mollicutes evolved by regressive evolution and genome reduction from the genus Clostridium (for a review, see reference 15). The reduced genome of the mollicutes yields a minimal inventory of cellular components and extreme structural simplicity. Nonetheless, the cells have a well-defined shape, are chemotactic and motile, and demonstrate a variety of cell movements and dynamic morphologies. For example, mycoplasmas and acholeplasmas glide on solid and semisolid surfaces, while the spiroplasmas (2) are free swimmers (for a review, see reference 11).The mollicutes lack cell walls and flagella but have an internal, contractile cytoskeleton that functions as a linear motor (for a review, see reference 20). The spiroplasmas have a particularly unique cellular geometry, such that the Spiroplasma cell can be viewed as a membranous tube to which a flat cytoskeletal ribbon of parallel fibrils is attached along the shortest helical line on the inner surface of the cellular tube. Both tube and cytoskeleton are mutually coiled into a dynamic helix, the latter driving the former. The cytoskeletal ribbon functions as a linear motor by differentially changing the length of its fibril components (21).The genus Spiroplasma was first described by Saglio et al. (16). Williamson (25) and Williamson and Whitcomb (26) reported the isolation of Spiroplasma cytoskeletons by cell lysis and detergent extraction. It has also been shown that cytoskeletons can be released from Spiroplasma cells by repeated freezing and thawing (19). Further electron microscopy studies on Spiroplasma spp. (4,5,17,27) led to a model of a flat, polar, dense cytoskeletal ribbon ϳ94 nm wide attached to the inner surface of the cell membrane and constructed from ϳ4.5-to 5.0-nm-diameter fibrils with an ϳ9-nm repeat. The cytoskeleton accounts for ϳ1% of the total cell...

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Section: Resultssupporting

confidence: 48%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Vol 185 2003mentioning

confidence: 99%

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Mass Distribution and Spatial Organization of the Linear Bacterial Motor ofSpiroplasma citriR8A2

2003

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“…A Spiroplasma cell can be viewed as a membranous tube to which a flat cytoskeletal ribbon of parallel fibrils is attached along the shortest helical line on the inner surface of the tube [3]. An average cell of ~4 helical turns has a tube and coil diameter of ~0.2 and 0.6 µm, respectively, a period ~0.9 µm and a contour length of ~6 µm [4]. The average linearmass-density of a freeze-dried cell is ~3.74 MDa/nm (Fig 1a, 2a) and the total mass of an average cell is ~2.22×10 10 Da/cell, equivalent to ~3.69×10 -14 gram/cell.…”

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Mass Analysis of Individual Spiroplasma Cells and their Cytoskeletons

Trachtenberg

Brantner

Leapman

et al. 2005

MAM

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The mollicutes are wall-less bacteria that evolved by regressive evolution and genome reduction from the genus Clostridium [1]. They are the simplest free-living and self-replicating forms of life. Spiroplasma has helical symmetry [2] and an internal, contractile cytoskeleton that functions as a linear motor by differential contraction of its fibril components. Here we take advantage of this cell's helical geometry to quantify annular dark-field STEM images in terms of the mass and organization of whole cells and their cytoskeleton. A Spiroplasma cell can be viewed as a membranous tube to which a flat cytoskeletal ribbon of parallel fibrils is attached along the shortest helical line on the inner surface of the tube [3]. An average cell of ~4 helical turns has a tube and coil diameter of ~0.2 and 0.6 µm, respectively, a period ~0.9 µm and a contour length of ~6 µm [4]. The average linearmass-density of a freeze-dried cell is ~3.74 MDa/nm (Fig 1a, 2a) and the total mass of an average cell is ~2.22×10 10 Da/cell, equivalent to ~3.69×10 -14 gram/cell. The average mass density of a double layered, collapsed, cytosol-free, membrane vesicle is ~11.08 kDa/nm 2 (Fig 1b, 2b), while the linear mass density of individual cytoskeletal fibrils (Fig 1c, 2c) is 13.5 kDa/nm [5]. The number of fibrils per ribbon, deduced from the mass per length of straight, uniform ribbons divided by the linear mass density of individual fibrils, is therefore 13.8 (Fig 1c, 2d). The total mass of the cytoskeletal ribbon per average cell is ~1.12×10 6 Da, accounting for only 5% of the total cell mass. Diffraction patterns of a monolayered, cytoskeletal ribbon (Fig 1e) reveal axial and lateral repeats of ~1/8.7 and ~1/10.2 nm -1 , respectively. Cytoskeletal fibrils are assembled from a 59 kDa protein with an average volume per mass of 1.2×10 -3 nm 3 /Da and an equivalent sphere diameter of ~5.1 nm. This information, combined with the present results, support the following functional model: A 59 kDa protein occupies an average distance, F L , along a fibril with a measured linear mass density M L =13.5±0.2 kDa/nm of F L =MW/M L =4.36±0.06 nm. The number of monomers, N, contained within an axial repeat, P=8.7 nm, along a fibril is N=P/F L =1.99±0.03. Thus, we conclude that the basic structural repeat along the fibril is a dimer. The lateral repeat within a monolayered ribbon is ~10.2 nm corresponding to a pair of fibrils. The structural building block of the ribbon is a chain of dimers, while the functional unit is a pair of dimeric chains forming tetrameric rings. A total of ~14,000 molecules may be expected in the average cell. We suggest that generation of motive force involves a conformational change in the linked tetrameric subunit from a circular to elliptical arrangement, possibly with the participation of other proteins [6].

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Mycoplasma

Razin

2010

Topley &Amp; Wilson's Microbiology and Microbial Infections

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The bacterial linear motor of Spiroplasma melliferum BC3: from single molecules to swimming cells

Cited by 36 publications

References 29 publications

Mass Distribution and Spatial Organization of the Linear Bacterial Motor ofSpiroplasma citriR8A2

Mass Distribution and Spatial Organization of the Linear Bacterial Motor ofSpiroplasma citriR8A2

Mass Analysis of Individual Spiroplasma Cells and their Cytoskeletons

Mycoplasma

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