Structural analysis of Mycoplasma pneumoniae by cryo-electron tomography

Seybert, Anja; Herrmann, Richard; Frangakis, Achilleas S.

doi:10.1016/j.jsb.2006.04.010

Cited by 93 publications

(122 citation statements)

References 67 publications

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“…Although it remains to be determined whether the same applies for proteins known to be specifically associated with the electron-dense core, the inhibition of nascent terminal organelle formation in cells under chloramphenicol arrest is consistent with a requirement for new protein synthesis. This conclusion is likewise consistent with electron cryotomography images (14,15) in which the dimensions of the two rods of the core are not identical, and therefore fail to support a semiconservative process. Taken together these observations expand our current understanding of terminal organelle development but also raise questions regarding regulation of synthesis and assembly of this structure and the coordination of the process with cell division, particularly given the dearth of typical transcriptional regulators in M. pneumoniae (2).…”

Section: Discussionsupporting

confidence: 77%

“…Loss of certain cytadherence-accessory proteins results in failure to assemble a core or to exhibit the polarity characteristic of wild-type M. pneumoniae cells (10,11). By conventional electron microscopy of thin sections the electron-dense core appears as two parallel flattened rods (12,13) but recent analysis by electron cryotomography has revealed a complex, multisubunit composition to this structure (14,15). Nevertheless, little is known regarding its molecular architecture or functional mechanisms.…”

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confidence: 99%

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Terminal organelle development in the cell wall-less bacterium Mycoplasma pneumoniae

Hasselbring

Jordan

Krause

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Mycoplasmas are cell wall-less bacteria considered among the smallest and simplest prokaryotes known, and yet several species including Mycoplasma pneumoniae have a remarkably complex cellular organization highlighted by the presence of a differentiated terminal organelle, a membrane-bound cell extension distinguished by an electron-dense core. Adhesin proteins localize specifically to the terminal organelle, which is also the leading end in gliding motility. Duplication of the terminal organelle is thought to precede cell division, but neither the mechanism of its duplication nor its role in this process is understood. Here we used fluorescent protein fusions and time-lapse digital imaging to study terminal organelle formation in detail in growing cultures of M. pneumoniae. Individual cells ceased gliding as a new terminal organelle formed adjacent to an existing structure, which then migrated away from the transiently stationary nascent structure. Multiple terminal organelles often formed before cytokinesis was observed. The separation of terminal organelles was impaired in a nonmotile mutant, indicating a requirement for gliding in normal cell division. Examination of cells expressing two different fluorescent protein fusions concurrently established their relative order of appearance, and changes in the fluorescence pattern over time suggested that nascent terminal organelles originated de novo rather than from an existing structure. In summary, spatial and temporal analysis of terminal organelle formation has yielded insights into the nature of M. pneumoniae cell division and the role of gliding motility in that process.cell division ͉ gliding motility ͉ adherence ͉ fluorescent protein fusion M ycoplasma pneumoniae causes chronic infections of the human respiratory tract, including bronchitis and primary atypical or ''walking'' pneumonia, accounting for up to 30% of all community-acquired pneumonia, particularly among older children and young adults. M. pneumoniae infections can result in chronic or permanent lung damage, and a growing body of evidence supports a correlation with the onset, exacerbation, and recurrence of asthma. Furthermore, extrapulmonary sequelae are not uncommon, reflecting both invasive and immunopathological components to M. pneumoniae disease (1).In addition to its significant impact on public health, M. pneumoniae is intriguing from a biological perspective. Mycoplasmas have no cell wall and are among the smallest known cells, with M. pneumoniae having a cell volume only Ϸ5% of that of Escherichia coli. Likewise, at 816 kb the M. pneumoniae genome is among the smallest known for a cell capable of a free-living existence, lacking genes for cell wall production, de novo synthesis of nucleotides and amino acids, and twocomponent or other common bacterial transcriptional regulators (2, 3). Nevertheless, a remarkable level of structural complexity underlies what are otherwise considered minimal cells (4). Thus, experimental evidence indicated the presence of cytoskeletal structure and fu...

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Section: Discussionsupporting

confidence: 77%

mentioning

confidence: 99%

Terminal organelle development in the cell wall-less bacterium Mycoplasma pneumoniae

Hasselbring

Jordan

Krause

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…M. pneumoniae also glides by means of a membrane protrusion, named ''the attachment organelle,'' formed at a cell pole (2)(3)(4)(5)46). The attachment organelle is known to have a cytoskeletal structure functioning as the scaffold for machinery of adherence and gliding (8,31,32,41). This structure consists of three parts, a terminal button, rod, and wheel (bowl) from the distal end (42).…”

Section: Discussionmentioning

confidence: 99%

Cytoskeletal “jellyfish” structure of Mycoplasma mobile

Nakane

Miyata

2007

Proc. Natl. Acad. Sci. U.S.A.

119

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Mycoplasma mobile, a parasitic bacterium lacking a peptidoglycan layer, glides on solid surfaces in the direction of a membrane protrusion at a cell pole by a unique mechanism. Recently, we proposed a working model in which cells are propelled by leg proteins clustering at the protrusion's base. The legs repeatedly catch and release sialic acids on the solid surface, a motion that is driven by the force generated by ATP hydrolysis. Here, to clarify the subcellular structure supporting the gliding force and the cell shape, we stripped the membrane by Triton X-100 and identified a unique structure, designated the ''jellyfish'' structure. In this structure, an oval solid ''bell'' Ϸ235 wide and 155 nm long is filled with a 12-nm hexagonal lattice and connected to this structure are dozens of flexible ''tentacles'' that are covered with particles of 20-nm diameter at intervals of Ϸ30 nm. The particles appear to have 180°rotational symmetry and a dimple at the center. The relation of this structure to the gliding mechanism was suggested by its cellular localization and by analyses of mutants lacking proteins essential for gliding. We identified 10 proteins as the components by mass spectrometry and found that these do not show sequence similarities with other proteins of bacterial cytoskeletons or the gliding proteins previously identified. Immunofluorescence and immunoelectron microscopy revealed that two components are localized at the bell and another that has the structure similar to the F1-ATPase ␤ subunit is localized at the tentacles.bacteria ͉ electron microscopy ͉ gliding motility ͉ immunofluorescence ͉ protein identification M ycoplasmas are commensal and occasionally parasitic bacteria with small genomes that lack a peptidoglycan layer (1). Several mycoplasma species form membrane protrusions, such as the head-like structure in Mycoplasma mobile and the attachment organelle in Mycoplasma pneumoniae (2)(3)(4)(5)(6)(7)(8)46). On solid surfaces, these species exhibit gliding motility in the direction of the protrusion; this motility is believed to be involved in the pathogenicity of mycoplasmas (3-5, 9, 10, 46). Interestingly, mycoplasmas have no surface flagella or pili, and their genomes contain no genes related to known bacterial motility. In addition, no homologs of motor proteins that are common in eukaryotic motility have been found (3-5, 11, 46). M. mobile, isolated from the gills of a freshwater fish in the early 1980s, is a fast-gliding mycoplasma (12-16). It glides smoothly and continuously on glass at an average speed of 2.0 to 4.5 m/s, or three to seven times the length of the cell per second, exerting a force of up to 27 piconewtons (pN). Recently, we identified huge proteins involved in this gliding mechanism (17-21), visualized the putative machinery and the binding protein (22,23), and identified the direct energy source used and the direct binding target (24)(25)(26). On the basis of these results, we proposed a working model in which cells are propelled by ''legs'' composed of Gli349 repeated...

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“…Proper assembly of the core is essential for formation of a functional attachment organelle (Krause & Balish, 2004), making the core essential for virulence. The core consists of several subdomains, including a distal terminal button which is probably in direct contact with the attachment organelle tip, a perpendicularly striated double rod, and a proximal complex that includes a bowl-shaped component at the base (Henderson & Jensen, 2006;Seybert et al, 2006). Although studies of M. pneumoniae attachment organelle mutants have led to the identification of many attachment organelle proteins and to the outline of an assembly pathway (Krause & Balish, 2004), how each protein contributes to the structure of the core remains poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Attachment organelle ultrastructure correlates with phylogeny, not gliding motility properties, in Mycoplasma pneumoniae relatives

Hatchel

Balish

2008

Microbiology

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The Mycoplasma pneumoniae cluster is a clade of eight described species which all exhibit cellular polarity. Their polar attachment organelle is a hub of cellular activities including cytadherence and gliding motility, and its duplication in the species M. pneumoniae is coordinated with cell division and DNA replication. The attachment organelle houses a detergent-insoluble, electron-dense core whose presence is required for structural integrity. Although mutant analysis has led to the identification of attachment organelle proteins, the mechanistic basis for the activities of the attachment organelle remains poorly understood, with gliding motility attributed alternatively to the core or to the adhesins. In this study we investigated attachment organelle-associated phenotypes, including gliding motility characteristics and ultrastructural details, in seven species of the M. pneumoniae cluster under identical conditions, allowing direct comparison. We identified gliding ability in three species in which it has not previously been reported, Mycoplasma imitans, Mycoplasma pirum and Mycoplasma testudinis. Across species, ultrastructural features of attachment organelles and their cores do not correlate with gliding speed, and morphological features of cores are inconsistent with predictions about how these structures are involved in the gliding process, disfavouring a prominent, direct role for the electron-dense core in gliding. In addition, we found M. pneumoniae to be an outlier in terms of cell structure with respect to its close relatives, suggesting that it has acquired a special set of adaptations during its evolution.

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Structural analysis of Mycoplasma pneumoniae by cryo-electron tomography

Cited by 93 publications

References 67 publications

Terminal organelle development in the cell wall-less bacterium Mycoplasma pneumoniae

Terminal organelle development in the cell wall-less bacterium Mycoplasma pneumoniae

Cytoskeletal “jellyfish” structure of Mycoplasma mobile

Attachment organelle ultrastructure correlates with phylogeny, not gliding motility properties, in Mycoplasma pneumoniae relatives

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