title: Proton gradients in intact cyanobacteria.
abstract: The internal pH values of two unicellular cyanobacterial strains were determined with electron spin resonance probes, over an external pH range of 6 to 9, in the light and in the dark.  The slow growing, thylakoid-lacking Gloeobacter violaceus was found to have a low capacity for maintaining a constant internal pH.  The distribution pattern of weak acid and amine nitroxide spin probes across the cell membranes of this organism, in the light and in the dark, was consistent with the assumption that it contains a single intracellular compartment.  At an external pH of 7.0, intracellular pH was 6.8 in the dark and 7.2 in the light.  The cells of Agmenellum quadruplicatum, a marine species, were found to contain two separate compartments; in the dark, the pH of the cytoplasmic and the intrathylakoid spaces were calculated to be 7.2 and 5.5, respectively.  Upon illumination, the former increased and the latter decreased by about 0.5 pH units.
authors.affiliation: Department of Physiology-Anatomy, Lawrence Berkeley Laboratory, University of California, Berkeley 94720, USA.
authors.forename: S
authors.initials: S
authors.lastname: Belkin
authors.forename: R J
authors.initials: RJ
authors.lastname: Mehlhorn
authors.forename: L
authors.initials: L
authors.lastname: Packer
mesh_terms: D001692:Biological Transport / Q000502:physiology; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D000458:Cyanobacteria / Q000166:cytology* / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D003593:Cytoplasm / Q000502:physiology; D004563:Electrochemistry; D004734:Energy Metabolism / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008027:Light; D017440:Photoperiod; D011522:Protons
chemical_list: D011522:Protons