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Cell volume regulation in Mycoplasma gallisepticum
Abstract:
Mycoplasma gallisepticum cells incubated in 250 mM NaCl solutions in the absence of glucose showed a progressive fall in intracellular ATP concentration over a period of 2 to 3 h. When the ATP level fell below 40 microM the cell began to swell and become progressively permeable to [14C]inulin and leak intracellular protein and nucleotides. The addition of nondiffusable substances such as MgSO4 or disaccharides prevented swelling, suggesting that NaCl (and water) entry was due to Gibbs-Donnan forces. The addition of glucose after the initiation of cell swelling increased intracellular ATP, induced cell shrinkage, and prevented the release of intracellular components. The ATPase inhibitor dicyclohexylcarbodiimide, which collapsed the chemical and electrical components of the proton motive force, caused rapid cell swelling in the presence of glucose (and high intracellular ATP levels). Extracellular impermeable solutes such as MgSO4 and disaccharides prevented swelling of dicyclohexylcarbodiimide-treated cells incubated in NaCl. It was postulated that Na+ that diffused into the cell was extruded by an electrogenic Na+-H+ exchange (antiport) energized by the proton motive force established by the dicyclohexylcarbodiimide-sensitive H+-ATPase.
Insights
High salt conditions deplete ATP in Mycoplasma gallisepticum, causing cell swelling and leakage. Glucose addition restores ATP, reverses swelling, and prevents component loss, highlighting ATP
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Mycoplasma gallisepticum is a significant avian pathogen.
- Cellular homeostasis is crucial for bacterial survival and function.
- Understanding osmotic stress responses is vital for pathogen control.
Purpose of the Study:
- To investigate the effects of hyperosmotic stress on Mycoplasma gallisepticum.
- To elucidate the role of intracellular ATP and ion transport in cell volume regulation.
- To identify potential targets for antimicrobial intervention.
Main Methods:
- Incubation of M. gallisepticum in high NaCl concentrations.
- Measurement of intracellular ATP levels.
- Assessment of cell permeability using [14C]inulin.
- Analysis of intracellular component leakage.
- Use of ATPase inhibitors and impermeable solutes.
Main Results:
- High NaCl caused a decrease in intracellular ATP, leading to cell swelling and permeability.
- Non-diffusible solutes prevented swelling, indicating Gibbs-Donnan forces.
- Glucose addition restored ATP, induced shrinkage, and prevented leakage.
- Dicyclohexylcarbodiimide (DCCD) induced swelling, even with high ATP, suggesting proton motive force involvement.
Conclusions:
- Intracellular ATP depletion is a key factor in osmotic stress-induced cell damage in M. gallisepticum.
- Na+ influx and subsequent extrusion via an electrogenic Na+-H+ antiport, energized by proton motive force, regulate cell volume.
- Targeting the H+-ATPase or Na+-H+ exchange could be a strategy to combat M. gallisepticum infections.
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