title: Changes in phosphorylation of adenosine phosphate and redox state of nicotinamide-adenine dinucleotide (phosphate) in Geobacter sulfurreducens in response to electron acceptor and anode potential variation.
abstract: Geobacter sulfurreducens is one of the dominant bacterial species found in biofilms growing on anodes in bioelectrochemical systems. The intracellular concentrations of reduced and oxidized forms of nicotinamide-adenine dinucleotide (NADH and NAD(+), respectively) and nicotinamide-adenine dinucleotide phosphate (NADPH and NADP(+), respectively) as well as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) were measured in G. sulfurreducens using fumarate, Fe(III)-citrate, or anodes poised at different potentials (110, 10, -90, and -190 mV (vs. SHE)) as the electron acceptor. The ratios of CNADH/CNAD+ (0.088±0.022) and CNADPH/CNADP+ (0.268±0.098) were similar under all anode potentials tested and with Fe(III)-citrate (reduced extracellularly). Both ratios significantly increased with fumarate as the electron acceptor (0.331±0.094 for NAD and 1.96±0.37 for NADP). The adenylate energy charge (the fraction of phosphorylation in intracellular adenosine phosphates) was maintained near 0.47 under almost all conditions. Anode-growing biofilms demonstrated a significantly higher molar ratio of ATP/ADP relative to suspended cultures grown on fumarate or Fe(III)-citrate. These results provide evidence that the cellular location of reduction and not the redox potential of the electron acceptor controls the intracellular redox potential in G. sulfurreducens and that biofilm growth alters adenylate phosphorylation.
authors: College of Engineering, Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, State College, PA 16802, USA. Electronic address: nrose@firstenvironment.com.
authors: Nicholas D
authors: ND
authors: Rose
authors: College of Engineering, Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, State College, PA 16802, USA. Electronic address: jregan@engr.psu.edu.
authors: John M
authors: JM
authors: Regan
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism*; D000249:Adenosine Monophosphate / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development; D004566:Electrodes; D004579:Electron Transport; D005290:Ferric Compounds / Q000378:metabolism; D005650:Fumarates / Q000378:metabolism; D045302:Geobacter / Q000378:metabolism* / Q000502:physiology; D009249:NADP / Q000378:metabolism*; D010766:Phosphorylation
chemical_list: D000227:Adenine Nucleotides; D005290:Ferric Compounds; D005650:Fumarates; D000249:Adenosine Monophosphate; D009249:NADP; C025314:ferric citrate; C032005:fumaric acid
keywords: Adenosine phosphate; Geobacter sulfurreducens; Nicotinamide adenine dinucleotide; Redox potential