title: Proton motive force in Rhodobacter sphaeroides under anaerobic conditions in the dark.
abstract: In order to examine the mediatory role of proton motive force (∆p) or proton ATPase in H₂ production by Rhodobacter sphaeroides, ∆p was determined under anaerobic conditions in the dark, and the ATPase activity has been studied in R. sphaeroides strain A-10, isolated from Arzni mineral springs in Armenia. Membrane potential (∆φ) was measured from the distribution of tetraphenylphosphonium cation; pH gradient (∆pH) was the difference between the external and cytoplasmic pH values, and the latter was measured by 9-aminoacridine (9-AA) fluorescence changes. At pH 7.5, ∆φ was of -94 mV and the reversed ∆pH was +30 mV, resulting in ∆p of -64 mV. The addition of N,N'-dicyclohexylcarbodiimide (DCCD), the F₀F₁-ATPase inhibitor, was not affect ∆φ. It was shown that ∆φ varies nearly linearly with ΔpH, ∆φ increased from -57.1 mV at pH 6.0 to -103.8 mV at pH 8.0; it was compensated at high external pH by a reversed ∆pH, resulting in a low ∆p under anaerobic-dark conditions. Intracellular ATP concentrations and energetic charge (EC) were measured to evaluate a metabolism activity of R. sphaeroides.
authors.affiliation: Department of Biophysics, Biological Faculty, Yerevan State University, 1 Alex Manoukian Str, 0025, Yerevan, Armenia.
authors.forename: Lilit
authors.initials: L
authors.lastname: Hakobyan
authors.forename: Lilit
authors.initials: L
authors.lastname: Gabrielyan
authors.forename: Armen
authors.initials: A
authors.lastname: Trchounian
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000693:Anaerobiosis; D001136:Armenia; D002462:Cell Membrane / Q000502:physiology; D003624:Darkness; D006859:Hydrogen / Q000378:metabolism; D008564:Membrane Potentials; D017494:Proton Pumps / Q000378:metabolism; D018892:Proton-Motive Force; D012242:Rhodobacter sphaeroides / Q000302:isolation & purification / Q000378:metabolism*; D014871:Water Microbiology
chemical_list: D017494:Proton Pumps; D006859:Hydrogen; D000251:Adenosine Triphosphatases