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Intracellular, periodic structures in the gliding bacterium Myxococcus xanthus
Abstract:
Electron microscopic observations of thin sections of Myxococcus xanthus vegetative cells revealed the presence of cytoplasmic bundles of 4- to 5-nm-diameter filaments running longtitudinally below the cell membrane and terminating in association with the envelope near one pole. Part of each bundle demonstrated a herringbone-like periodicity (approximately 12-nm spacing). This structure was observed in cells from shake cultures and in gliding cells fixed by several methods. It is proposed that the structure may be attached to the envelope near both poles in gliding cells and that the motive force for motility may be provided by its contraction and relaxation. In one of four nongliding mutants examined, the periodicity was indistinct or lacking. In this mutant another structure, comprised of linearly arrayed beads, was observed in association with the filamentous bundle. Another structure, characterized by major, transverse bands (approximately 34 nm apart), occurred in patches that may traverse the diameter of the wild-type cells in which the structure was observed.
Insights
Electron microscopy revealed novel cytoplasmic filaments in Myxococcus xanthus, potentially driving cell motility through contraction and relaxation. A related beaded structure was observed in non-motile mutants.
Area of Science:
- Microbiology
- Cell Biology
- Biophysics
Background:
- Myxococcus xanthus is a model organism for studying bacterial motility.
- The precise mechanism of gliding motility in M. xanthus remains incompletely understood.
- Cytoplasmic structures potentially involved in motility have been hypothesized but not definitively identified.
Purpose of the Study:
- To investigate the ultrastructure of Myxococcus xanthus vegetative cells using electron microscopy.
- To identify and characterize novel cytoplasmic structures potentially related to cell motility.
- To explore the relationship between observed structures and the gliding phenotype.
Main Methods:
- Transmission electron microscopy of thin-sectioned Myxococcus xanthus vegetative cells.
- Observation of cells from both shake cultures and actively gliding populations.
- Fixation of cells using multiple methods to ensure structural integrity.
- Examination of wild-type and non-gliding mutant strains.
Main Results:
- Cytoplasmic bundles of 4- to 5-nm filaments were observed longitudinally below the cell membrane, terminating near the cell envelope.
- A herringbone-like periodicity (approx. 12 nm spacing) was noted within these filamentous bundles.
- In a non-gliding mutant, this periodicity was indistinct, and a novel beaded structure was observed.
- Another structure with transverse bands (approx. 34 nm apart) was seen in patches in wild-type cells.
Conclusions:
- The observed filamentous bundles may be involved in Myxococcus xanthus motility, possibly by attaching to the cell envelope and generating force through contraction/relaxation.
- The distinct structural alterations in the non-gliding mutant suggest a role for these filaments in motility.
- Further research is warranted to elucidate the exact function and composition of these novel structures in bacterial gliding.