Mollicutes—Wall-less Bacteria with Internal Cytoskeletons

Trachtenberg, Shlomo

doi:10.1006/jsbi.1998.4063

Cited by 82 publications

(68 citation statements)

References 109 publications

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“…Although mycoplasmas lack a peptidoglycan layer, many species have cell shapes other than spherical, such as conical, filamentous, and spiral. These special shapes are believed to be maintained by filamentous protein structures (35). Filamentous structures of M. pneumoniae can be seen in a Triton-insoluble fraction (11,24).…”

Section: Discussionmentioning

confidence: 99%

Force and Velocity of Mycoplasma mobile Gliding

2002

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The effects of temperature and force on the gliding speed of Mycoplasma mobile were examined. Gliding speed increased linearly as a function of temperature from 0.46 m/s at 11.5°C to 4.0 m/s at 36.5°C. A polystyrene bead was attached to the tail of M. mobile using a polyclonal antibody raised against whole M. mobile cells. Cells attached to beads glided at the same speed as cells without beads. When liquid flow was applied in a flow chamber, cells reoriented and moved upstream with reduced speeds. Forces generated by cells at various gliding speeds were calculated by multiplying their estimated frictional drag coefficients with their velocities relative to the liquid. The gliding speed decreased linearly with force. At zero speed, the force measurements extrapolated to 26 pN at 22.5 and 27.5°C. At zero force, the speed extrapolated to 2.3 and 3.3 m/s at 22.5 and 27.5°C, respectively-the same speeds as those observed for free gliding cells. Cells attached to beads were also trapped by an optical tweezer, and the stall force was measured to be 26 to 28 pN (17.5 to 27.5°C). The gliding speed depended on temperature, but the maximum force did not, suggesting that the mechanism is composed of at least two steps, one that generates force and another that allows displacement. Other implications of these results are discussed.Mycoplasmas are parasitic bacteria with a small genome and no peptidoglycan layer (27). Several mycoplasma species have a distinct cell polarity characterized by a protruding membrane extension, the attachment organelle (27). They are able to attach to and glide on glass, plastic, and eukaryotic cell surfaces, always moving in the direction of the organelle (19). The gliding mechanism is unknown. Mycoplasmas do not have any appendages such as flagella or pili (19) or any genes obviously related to motility, including motor proteins such as myosin or kinesin (7, 10, 13). However, a transmembrane protein associated with a cytoskeleton-like structure has been shown to be necessary for glass binding in Mycoplasma pneumoniae (22).Mycoplasma mobile, isolated from a fish gill organ, has a conical cell structure, with the attachment organelle at the apex of the cone. It glides up to four cell lengths per second (2.5 m/s) in the direction of the apex, which is designated as a head-like structure (30). However, little is known about force generation (28,29). In this study, to characterize its gliding motility, we attached a bead to the tail end of M. mobile and measured the gliding force as a function of speed using viscous flow and an optical tweezer. MATERIALS AND METHODSCultivation. M. mobile strain 163K (ATCC 43663) was grown as described previously (25).Measurements of gliding speed. M. mobile cells in a culture at an optical density at 600 nm of 0.03 to 0.1 were collected by centrifugation at 10,000 ϫ g for 4 min at room temperature and resuspended in a fivefold-smaller volume of medium. A 5-l aliquot was sealed between a coverslip and a slide within a thin ring of Apiezon M grease (Apiezon Products, L...

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Section: Discussionmentioning

confidence: 99%

Force and Velocity of Mycoplasma mobile Gliding

2002

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“…Although there had been previous indications of organized structures within bacterial cells (18,139,209), including the demonstration by Bi and Lutkenhaus that the tubulin homolog FtsZ forms a ring-like structure at the division site (15), the period of rapid advance began with the discovery by Jones et al in 2001 that bacterial actin homologs in Bacillus subtilis are organized into extended helical structures that play key roles in cell shape regulation (95). Since then, the dictum that bacteria have no long-range internal structure has been replaced by the realization that the interior of the bacterial cell contains a large number of organized cytoskeletal elements, probably with a much larger group of cytoskeleton-associated components still to be discovered.…”

Section: Introductionmentioning

confidence: 99%

The Bacterial Cytoskeleton

Shih

Rothfield

2006

Microbiol Mol Biol Rev

238

220

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SUMMARY In recent years it has been shown that bacteria contain a number of cytoskeletal structures. The bacterial cytoplasmic elements include homologs of the three major types of eukaryotic cytoskeletal proteins (actin, tubulin, and intermediate filament proteins) and a fourth group, the MinD-ParA group, that appears to be unique to bacteria. The cytoskeletal structures play important roles in cell division, cell polarity, cell shape regulation, plasmid partition, and other functions. The proteins self-assemble into filamentous structures in vitro and form intracellular ordered structures in vivo. In addition, there are a number of filamentous bacterial elements that may turn out to be cytoskeletal in nature. This review attempts to summarize and integrate the in vivo and in vitro aspects of these systems and to evaluate the probable future directions of this active research field.

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“…Over the past 20 years, indications have accumulated that M. pneumoniae possesses a cytoskeleton-like structure, probably as a substitute for the missing cell wall (Biberfeld & Biberfeld, 1970 ;Go$ bel et al, 1981 ;Krause et al, 1982 ;Meng & Pfister, 1980 ;Wilson & Collier, 1976). By analogy with eukaryotic cells, such a cytoskeleton could provide the necessary framework for maintaining and stabilizing the shape of M. pneumoniae (Trachtenberg, 1998), for motility (Radestock & Bredt, 1977) and for the formation of an asymmetric cell. Cell asymmetry is related to the attachment organelle, a membrane-bound extension of the cell.…”

Section: Introductionmentioning

confidence: 99%

Defining the mycoplasma ‘cytoskeleton’: the protein composition of the Triton X-100 insoluble fraction of the bacterium Mycoplasma pneumoniae determined by 2-D gel electrophoresis and mass spectrometry

et al. 2001

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After treating Mycoplasma pneumoniae cells with the nonionic detergent Triton X-100, an undefined, structured protein complex remains that is called the ' Triton X-100 insoluble fraction ' or ' Triton shell '. By analogy with eukaryotic cells and supported by ultrastructural analyses it is supposed that this fraction contains the components of a bacterial cytoskeleton-like structure. In this study, the composition of the Triton X-100 insoluble fraction was defined by electron microscopic screening for possible structural elements, and by two-dimensional (2-D) gel electrophoresis and MS to identify the proteins present. Silver staining of 2-D gels revealed about 100 protein spots. By staining with colloidal Coomassie blue, about 50 protein spots were visualized, of which 41 were identified by determining the mass and partial sequence of tryptic peptides of individual proteins. The identified proteins belonged to several functional categories, mainly energy metabolism, translation and heat-shock response. In addition, lipoproteins were found and most of the proteins involved in cytadherence that were previously shown to be components of the Triton X-100 insoluble fraction. There were also 11 functionally unassigned proteins. Based on sequence-derived predictions, some of these might be potential candidates for structural components. Quantitatively, the most prevalent proteins were the heat-shock protein DnaK, elongation factor Tu and subunits α and β of the pyruvate dehydrogenase complex (PdhA, PdhB), but definite conclusions regarding the composition of the observed structures can only be drawn after specific proteins are assigned to them, for example by immunocytochemistry.

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Mollicutes—Wall-less Bacteria with Internal Cytoskeletons

Cited by 82 publications

References 109 publications

Force and Velocity of Mycoplasma mobile Gliding

Force and Velocity of Mycoplasma mobile Gliding

The Bacterial Cytoskeleton

Defining the mycoplasma ‘cytoskeleton’: the protein composition of the Triton X-100 insoluble fraction of the bacterium Mycoplasma pneumoniae determined by 2-D gel electrophoresis and mass spectrometry

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