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Proton gradients in intact cyanobacteria
S Belkin1, R J Mehlhorn, L Packer
1Department of Physiology-Anatomy, Lawrence Berkeley Laboratory, University of California, Berkeley 94720, USA.
Plant Physiology
|January 1, 1987
Summary
Electron spin resonance probes revealed that cyanobacteria internal pH varies. Gloeobacter violaceus struggles to maintain pH, while Agmenellum quadruplicatum shows distinct cytoplasmic and intrathylakoid pH levels that change with light.
Area of Science:
- Microbiology
- Biochemistry
- Cell Biology
Background:
- Cyanobacteria are vital microorganisms with diverse physiological adaptations.
- Internal pH regulation is crucial for cellular functions and survival.
- Understanding pH homeostasis in different cyanobacterial species provides insights into their ecological roles.
Purpose of the Study:
- To determine and compare the intracellular pH regulation capabilities of two distinct unicellular cyanobacterial strains.
- To investigate the influence of light and dark conditions on internal pH in these organisms.
- To elucidate the compartmentalization of pH within cyanobacterial cells.
Main Methods:
- Utilized electron spin resonance (ESR) probes for non-invasive internal pH measurements.
- Examined pH across an external pH range of 6 to 9.
- Assessed pH changes under both light and dark conditions.
Main Results:
- Gloeobacter violaceus, a thylakoid-lacking strain, demonstrated a limited capacity for maintaining a stable internal pH.
- The distribution of spin probes in G. violaceus suggested a single intracellular compartment.
- Agmenellum quadruplicatum, a marine species, exhibited two distinct compartments with different pH values (cytoplasmic and intrathylakoid).
- In A. quadruplicatum, illumination caused a ~0.5 unit increase in cytoplasmic pH and a similar decrease in intrathylakoid pH.
Conclusions:
- Internal pH regulation varies significantly between different cyanobacterial species.
- G. violaceus appears to have a simpler intracellular structure regarding pH compartmentalization.
- A. quadruplicatum possesses a more complex pH regulatory system, with light-dependent modulation of pH in separate compartments.