Generation of a proton motive force by the anaerobic oxalate-degrading bacterium Oxalobacter formigenes

• Published in: Applied and Environmental Microbiology 1996-07, Vol.62 (7), p.2494-2500
• Main Authors: Kuhner, C.H. (Iowa State University, Ames, IA.), Hartman, P.A, Allison, M.J
• Format: Article
• Language: English
• Subjects: ACIDE OXALIQUE; ACIDO OXALICO; ANAEROBIOSE; ANAEROBIOSIS; BACTERIA; Bacteriology; Biodegradation, Environmental; Biological and medical sciences; CATION; CATIONES; Dicyclohexylcarbodiimide - pharmacology; Energy Metabolism; Enzyme Inhibitors - pharmacology; ESTRUCTURA CELULAR; Fundamental and applied biological sciences. Psychology; Gram-Negative Anaerobic Bacteria - cytology; Gram-Negative Anaerobic Bacteria - drug effects; Gram-Negative Anaerobic Bacteria - metabolism; HIDROGENO; Hydrogen-Ion Concentration; HYDROGENE; ION; Ion Transport; IONES; Ionophores - pharmacology; Ions; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; Membrane Potentials; Metabolism; Metabolism. Enzymes; METABOLISME; METABOLISMO; Microbiology; MICROORGANISME; MICROORGANISME DU RUMEN; MICROORGANISMOS; MICROORGANISMOS DEL RUMEN; Monensin - pharmacology; Oxalates - metabolism; Oxalic Acid; Oxalobacter formigenes; Oxidation; POTENCIAL ELECTRICO; POTENTIEL ELECTRIQUE; Proton-Motive Force; Proton-Translocating ATPases - antagonists & inhibitors; Protons; STRUCTURE CELLULAIRE; Valinomycin - pharmacology
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.62.7.2494-2500.1996

The generation of transmembrane ion gradients by Oxalobacter formigenes cells metabolizing oxalate was studied. The magnitudes of both the transmembrane electrical potential and the pH gradient (internal alkaline) decreased with increasing external pH; quantitatively, the transmembrane electrical potential was the most important component of the proton motive force. As the extracellular pH of metabolizing cells was increased, intracellular pH increased and remained alkaline relative to the external pH, indicating that O. formigenes possesses a limited capacity to regulate internal pH. The generation of a transmembrane electrical potential by concentrated suspensions of O. formigenes cells was inhibited by the K+ ionophore valinomycin and the protonophore carbonyl cyanide-m-chlorophenylhydrazone, but not by the Na+ ionophore monensin. The H+ ATPase inhibitor N,N'-dicyclohexyl-carbodiimide inhibited oxalate catabolism but did not dissipate the transmembrane electrical potential. The results support the concept that energy from oxalate metabolism by O. formigenes is conserved not as a sodium ion gradient but rather, at least partially, as a transmembrane hydrogen ion gradient produced during the electrogenic exchange of substrate (oxalate) and product (formate) and from internal proton consumption during oxalate decarboxylation