Metabolic response of Geobacter sulfurreducens towards electron donor/acceptor variation

Microb Cell Fact. 2010 Nov 22;9:90. doi: 10.1186/1475-2859-9-90.

Abstract

Background: Geobacter sulfurreducens is capable of coupling the complete oxidation of organic compounds to iron reduction. The metabolic response of G. sulfurreducens towards variations in electron donors (acetate, hydrogen) and acceptors (Fe(III), fumarate) was investigated via (13)C-based metabolic flux analysis. We examined the (13)C-labeling patterns of proteinogenic amino acids obtained from G. sulfurreducens cultured with (13)C-acetate.

Results: Using (13)C-based metabolic flux analysis, we observed that donor and acceptor variations gave rise to differences in gluconeogenetic initiation, tricarboxylic acid cycle activity, and amino acid biosynthesis pathways. Culturing G. sulfurreducens cells with Fe(III) as the electron acceptor and acetate as the electron donor resulted in pyruvate as the primary carbon source for gluconeogenesis. When fumarate was provided as the electron acceptor and acetate as the electron donor, the flux analysis suggested that fumarate served as both an electron acceptor and, in conjunction with acetate, a carbon source. Growth on fumarate and acetate resulted in the initiation of gluconeogenesis by phosphoenolpyruvate carboxykinase and a slightly elevated flux through the oxidative tricarboxylic acid cycle as compared to growth with Fe(III) as the electron acceptor. In addition, the direction of net flux between acetyl-CoA and pyruvate was reversed during growth on fumarate relative to Fe(III), while growth in the presence of Fe(III) and acetate which provided hydrogen as an electron donor, resulted in decreased flux through the tricarboxylic acid cycle.

Conclusions: We gained detailed insight into the metabolism of G. sulfurreducens cells under various electron donor/acceptor conditions using (13)C-based metabolic flux analysis. Our results can be used for the development of G. sulfurreducens as a chassis for a variety of applications including bioremediation and renewable biofuel production.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetic Acid / chemistry
  • Acetic Acid / metabolism
  • Acetyl Coenzyme A / metabolism
  • Amino Acids / biosynthesis
  • Amino Acids / metabolism
  • Carbon Isotopes / chemistry
  • Citric Acid Cycle
  • Electrons*
  • Ferric Compounds / chemistry
  • Fumarates / chemistry
  • Fumarates / metabolism
  • Geobacter / growth & development
  • Geobacter / metabolism*
  • Gluconeogenesis
  • Oxidation-Reduction
  • Phosphoenolpyruvate Carboxykinase (GTP) / metabolism
  • Pyruvates / metabolism

Substances

  • Amino Acids
  • Carbon Isotopes
  • Ferric Compounds
  • Fumarates
  • Pyruvates
  • Acetyl Coenzyme A
  • Phosphoenolpyruvate Carboxykinase (GTP)
  • Acetic Acid