Topic
Cell envelope organization
About: Cell envelope organization is a research topic. Over the lifetime, 5 publications have been published within this topic receiving 663 citations.
Papers
TL;DR: Cryo-transmission electron microscopy of frozen-hydrated sections of Staphylococcus aureus D2C was used to examine cell envelope organization and results strongly indicate that the IWZ represents a periplasmic space, composed mostly of soluble low-density constituents confined between the plasma membrane and OWZ, and that the OWZ represents the peptidoglycan-teichoic acid cell wall network with its associated proteins.
Abstract: The current perception of the ultrastructure of gram-positive cell envelopes relies mainly on electron microscopy of thin sections and on sample preparation. Freezing of cells into a matrix of amorphous ice (i.e., vitrification) results in optimal specimen preservation and allows the observation of cell envelope boundary layers in their (frozen) hydrated state. In this report, cryo-transmission electron microscopy of frozen-hydrated sections of Staphylococcus aureus D2C was used to examine cell envelope organization. A bipartite wall was positioned above the plasma membrane and consisted of a 16-nm low-density inner wall zone (IWZ), followed by a 19-nm high-density outer wall zone (OWZ). Observation of plasmolyzed cells, which were used to artificially separate the membrane from the wall, showed membrane vesicles within the space associated with the IWZ in native cells and a large gap between the membrane and OWZ, suggesting that the IWZ was devoid of a cross-linked polymeric cell wall network. Isolated wall fragments possessed only one zone of high density, with a constant level of density throughout their thickness, as was previously seen with the OWZs of intact cells. These results strongly indicate that the IWZ represents a periplasmic space, composed mostly of soluble low-density constituents confined between the plasma membrane and OWZ, and that the OWZ represents the peptidoglycan-teichoic acid cell wall network with its associated proteins. Cell wall differentiation was also seen at the septum of dividing cells. Here, two high-density zones were sandwiched between three low-density zones. It appeared that the septum consisted of an extension of the IWZ and OWZ from the outside peripheral wall, plus a low-density middle zone that separated adjacent septal cross walls, which could contribute to cell separation during division.
220 citations
TL;DR: By labeling surface carbohydrates, it is found that a pool of lipoglycans, cell wall associated, is exposed at the cell surface of mycobacteria and thus, most probably, inserted in the outer leaflet of the outer membrane.
113 citations
TL;DR: Rickettsia tsutsugamushi differs from other rickettsiae in its cell envelope organization through a comparative study of the outer envelope of R. tsutsUGamushi, R. prowazekii, and R. ricksettsii by electron microscopy.
Abstract: Rickettsia tsutsugamushi differs from other rickettsiae in its cell envelope organization. The differences were made evident through a comparative study of the outer envelope of R. tsutsugamushi, R. prowazekii, and R. rickettsii by electron microscopy. Images
99 citations
TL;DR: It is shown that in Escherichia coli the low-order oligomeric PspA regulatory complex associates with cardiolipin-rich, curved polar inner membrane regions, and the consequences of loss of cytoplasmic membrane anionic lipids, MreB, RodZ and/or YqiK suggest that the mode of action of the PSPA effector is closely associated with cell envelope organization.
Abstract: All cell types must maintain the integrity of their membranes. The conserved bacterial membrane-associated protein PspA is a major effector acting upon extracytoplasmic stress and is implicated in protection of the inner membrane of pathogens, formation of biofilms and multi-drug-resistant persister cells. PspA and its homologues in Gram-positive bacteria and archaea protect the cell envelope whilst also supporting thylakoid biogenesis in cyanobacteria and higher plants. In enterobacteria, PspA is a dual function protein negatively regulating the Psp system in the absence of stress and acting as an effector of membrane integrity upon stress. We show that in Escherichia coli the low-order oligomeric PspA regulatory complex associates with cardiolipin-rich, curved polar inner membrane regions. There, cardiolipin and the flotillin 1 homologue YqiK support the PspBC sensors in transducing a membrane stress signal to the PspA-PspF inhibitory complex. After stress perception, PspA high-order oligomeric effector complexes initially assemble in polar membrane regions. Subsequently, the discrete spatial distribution and dynamics of PspA effector(s) in lateral membrane regions depend on the actin homologue MreB and the peptidoglycan machinery protein RodZ. The consequences of loss of cytoplasmic membrane anionic lipids, MreB, RodZ and/or YqiK suggest that the mode of action of the PspA effector is closely associated with cell envelope organization.
25 citations
TL;DR: The new model of cell envelope organization is discussed with respect to the current knowledge on bacterial cell wall structure and function and possibly fills the entire space between the inner and outer membranes in the form of a periplasmic gel.
Abstract: Bacterial cell envelope ultrastructure was investigated both by the progressive lowering of temperature embedding technique and freeze-substitution, using conventional and scanning transmission electron microscopy. Comparison with standard embedding procedures revealed a new aspect of cell envelope structure in specimens at low temperatures. The envelope was delimited by an electron-dark layer, beneath which was a uniform matter-containing layer lying between the outer and inner membranes. There was no empty periplasmic space. Buoyant densities of isolated peptidoglycan obtained in Percoll (1.02 to 1.07 g ml-1) and CsCl2 (1.44 g ml-1) led to a calculated hydration of the peptidoglycan which was more than was previously assumed. Peptidoglycan therefore possibly fills the entire space between the inner and outer membranes in the form of a periplasmic gel. The new model of cell envelope organization is discussed with respect to the current knowledge on bacterial cell wall structure and function.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2014 | 1 |
| 2008 | 1 |
| 2006 | 1 |
| 1984 | 1 |
| 1978 | 1 |