Flux analysis of central metabolic pathways in Geobactermetallireducens during reduction of solubleFe(III)-NTA

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Applied and Environmental Microbiology

DOI:https://doi.org/10.1128/AEM.02986-06· OSTI ID:918684

Tang, Yinjie J; Chakraborty, Romy; Garcia-Martin, Hector; Chu, Jeannie; Hazen, Terry C; Keasling, Jay D

We analyzed the carbon fluxes in the central metabolism ofGeobacter metallireducens strain GS-15 using 13C isotopomer modeling.Acetate labeled in the 1st or 2nd position was the sole carbon source,and Fe-NTA was the sole terminal electron acceptor. The measured labeledacetate uptake rate was 21 mmol/gdw/h in the exponential growth phase.The resulting isotope labeling pattern of amino acids allowed an accuratedetermination of the in vivo global metabolic reaction rates (fluxes)through the central metabolic pathways using a computational isotopomermodel. The tracer experiments showed that G. metallireducens containedcomplete biosynthesis pathways for essential metabolism, and this strainmight also have an unusual isoleucine biosynthesis route (usingacetyl-CoA and pyruvate as the precursors). The model indicated that over90 percent of the acetate was completely oxidized to CO2 via a completetricarboxylic acid (TCA) cycle while reducing iron. Pyruvate carboxylaseand phosphoenolpyruvate carboxykinase were present under theseconditions, but enzymes in the glyoxylate shunt and malic enzyme wereabsent. Gluconeogenesis and the pentose phosphate pathway were mainlyemployed for biosynthesis and accounted for less than 3 percent of totalcarbon consumption. The model also indicated surprisingly highreversibility in the reaction between oxoglutarate and succinate. Thisstep operates close to the thermodynamic equilibrium possibly becausesuccinate is synthesized via a transferase reaction, and the conversionof oxoglutarate to succinate is a rate limiting step for carbonmetabolism. These findings enable a better understanding of therelationship between genome annotation and extant metabolic pathways inG. metallireducens.

• Research Organization: Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director. Office of Science. Biological andEnvironmental Research
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 918684
• Report Number(s): LBNL--63533; BnR: KP1102010
• Journal Information: Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 12 Vol. 73; ISSN AEMIDF; ISSN 0099-2240
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AMINO ACIDS
BINDING ENERGY
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBON
CARBON SOURCES
IN VIVO
METABOLISM
REACTION KINETICS
labeled acetate minimal medium isoleucine TCA cycle acetyl-CoAtransferase