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Respiratory-driven Na+ electrical potential in the bacterium Vitreoscilla
1Department of Biology, Illinois Institute of Technology, Chicago 60616.
Biochemistry
|May 15, 1990
Summary
Vitreoscilla bacteria generate a transmembrane electrical gradient (delta psi) using sodium ions (Na+). This study suggests a direct, respiratory-driven sodium pump, not an ATPase or antiporter, is responsible for this unique energy coupling.
Area of Science:
- Microbiology
- Bioenergetics
- Cellular Physiology
Background:
- Vitreoscilla, a Gram-negative bacterium, exhibits unique respiratory physiology.
- Sodium ions (Na+) are implicated as coupling cations in generating transmembrane electrical gradients (delta psi).
Purpose of the Study:
- To investigate the mechanism of Na+ involvement in delta psi generation in Vitreoscilla.
- To differentiate between potential Na+ transport systems coupled to respiration.
Main Methods:
- Measurement of delta psi in response to varying cation concentrations (Na+, Li+, choline) and protonophore (DTHB).
- Analysis of Na+ and H+ fluxes kinetics correlated with delta psi changes.
- Inhibition studies using cyanide, DCCD, arsenate, and potassium ions.
Main Results:
- High Na+ concentrations generated a significantly larger delta psi (-142 mV) compared to Li+ or choline.
- Delta psi formation and collapse kinetics correlated with Na+ fluxes, not H+ fluxes.
- Evidence ruled out a Na+-transporting ATPase and a Na+/H+ antiport system, supporting a primary Na+ pump.
Conclusions:
- Vitreoscilla utilizes a respiratory-driven primary Na+ pump for generating delta psi.
- This mechanism is distinct from Na+-ATPases and Na+/H+ antiporters.
- The findings reveal a unique bioenergetic strategy in Vitreoscilla respiration.