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Supramolecular structures in mycoplasmas
Abstract:
Mycoplasma pneumoniae cells treated with Triton X-100 showed a detergent-resistant cytoskeleton. This cytoskeleton consists of microfilaments which seem related to eukaryotic actin filaments, both morphologically and in some chemical properties, including specific staining by anti-actin antibodies and rhodamine-labeled phalloidin. The degree of homology, however, is still unclear. In motile cells the filaments form an irregular network in the cytoplasm of the cell body and a bundle in the frontal projection corresponding to the leading edge of the gliding cells. This particular arrangement may reflect different functions. The microfilaments could be isolated by differential centrifugation. Analysis of the microfilament fraction by SDS gel electrophoresis revealed five major polypeptide bands. One of these proteins, with a molecular weight of 42.5 kd, co-migrated with rabbit muscle actin. No filaments could be found in a nonmotile mutant, M-22.
Insights
Mycoplasma pneumoniae possesses a detergent-resistant cytoskeleton composed of microfilaments resembling eukaryotic actin. These filaments are crucial for motility, forming distinct structures in motile cells but absent in nonmotile mutants.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Mycoplasma pneumoniae is a bacterium known for its unique cellular structure and motility.
- The presence and function of cytoskeletal elements in prokaryotes are of significant interest.
- Eukaryotic actin filaments play critical roles in cell structure, motility, and division.
Purpose of the Study:
- To investigate the presence and nature of a cytoskeleton in Mycoplasma pneumoniae.
- To determine if the cytoskeletal components share similarities with eukaryotic actin.
- To explore the relationship between cytoskeletal structure and cell motility in Mycoplasma pneumoniae.
Main Methods:
- Treatment of Mycoplasma pneumoniae cells with Triton X-100 to isolate detergent-resistant structures.
- Morphological and chemical characterization of the cytoskeleton, including staining with anti-actin antibodies and rhodamine-labeled phalloidin.
- Isolation of microfilaments via differential centrifugation and analysis by SDS gel electrophoresis.
- Comparison of isolated proteins with known standards, such as rabbit muscle actin.
Main Results:
- A detergent-resistant cytoskeleton was identified in Mycoplasma pneumoniae cells.
- The cytoskeleton consists of microfilaments exhibiting morphological and chemical similarities to eukaryotic actin, including positive staining with anti-actin antibodies and rhodamine-labeled phalloidin.
- A protein of 42.5 kDa co-migrated with rabbit muscle actin.
- These filaments were absent in a nonmotile mutant (M-22), suggesting a role in motility.
- Filament arrangement differed between the cell body and the leading edge of motile cells.
Conclusions:
- Mycoplasma pneumoniae possesses a cytoskeleton containing actin-like microfilaments.
- These microfilaments are likely involved in the motility of Mycoplasma pneumoniae.
- While showing similarities, the precise degree of homology between these bacterial microfilaments and eukaryotic actin requires further investigation.