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Membrane-bounded nucleoid in the eubacterium Gemmata obscuriglobus.
1Department of Microbiology, University of Queensland, Brisbane, Queensland, Australia.
Summary
The bacterium Gemmata obscuriglobus has a unique membrane-bound nucleoid, challenging the traditional prokaryote-eukaryote cell structure division. This discovery offers new insights into bacterial cell organization and evolution.
Area of Science:
- Microbiology
- Cell Biology
- Bacterial Ultrastructure
Background:
- The prokaryote-eukaryote dichotomy is a fundamental concept in cell biology.
- Eubacteria typically lack membrane-bound organelles, including a nucleus.
Purpose of the Study:
- To investigate the structural organization of the nucleoid in the eubacterium Gemmata obscuriglobus.
- To determine if Gemmata obscuriglobus possesses a membrane-bound nucleoid.
Main Methods:
- Thin sectioning of chemically fixed and freeze-substituted cells.
- Freeze-fracture/freeze-etch electron microscopy.
- Immunogold labeling with anti-double-stranded DNA antibody.
Main Results:
- Gemmata obscuriglobus exhibits a fibrillar nucleoid enclosed by two distinct nuclear membranes.
- An electron-transparent space separates the two nuclear membranes.
- Double-stranded DNA was localized within the membrane-bound region.
Conclusions:
- Gemmata obscuriglobus possesses a membrane-bounded nucleoid, which is a significant exception to typical eubacterial cell structure.
- This finding challenges the rigid prokaryote-eukaryote classification based on cell compartmentalization.
- The presence of a nucleoid suggests a more complex evolutionary pathway for certain bacteria.