Probing carbon flux patterns through soil microbial metabolic networks using parallel position-specific tracer labeling

Paul Dijkstra, Joseph C. Blankinship, Paul C. Selmants, Stephen C. Hart, George W. Koch, Egbert Schwartz, Bruce A. Hungate

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


In order to study controls on metabolic processes in soils, we determined the dynamics of 13CO2 production from two position-specific 13C-labeled pyruvate isotopologues in the presence and absence of glucose, succinate, pine, and legume leaf litter, and under anaerobic conditions. We also compared 13CO2 production in soils along a semiarid substrate age gradient in Arizona. We observed that the C from the carboxyl group (C1) of pyruvate was lost as CO2 much faster than its other C atoms (C2,3). Addition of glucose, pine and legume leaf litter reduced the ratio between 13CO2 production from 1-13C pyruvate and 2,3-13C pyruvate (C1/C2,3 ratio), whereas anaerobic conditions increased this ratio. Young volcanic soils exhibited a lower C1/C2,3 ratio than older volcanic soils. We interpret a low C1/C2,3 ratio as an indication of increased Krebs cycle activity in response to carbon inputs, while the higher ratio implies a reduced Krebs cycle activity in response to anaerobic conditions. Succinate, a gluconeogenic substrate, reduced 13CO2 production from pyruvate to near zero, likely reflecting increased carbohydrate biosynthesis from Krebs cycle intermediates. The difference in 13CO2 production rate from pyruvate isotopologues disappeared 4-5 days after pyruvate addition, indicating that C positions were scrambled by ongoing soil microbial transformations. This work demonstrates that metabolic tracers such as pyruvate can be used to determine qualitative aspects of C flux patterns through metabolic pathways of soil microbial communities. Understanding the controls over metabolic processes in soil may improve our understanding of soil C cycling processes.

Original languageEnglish (US)
Pages (from-to)126-132
Number of pages7
JournalSoil Biology and Biochemistry
Issue number1
StatePublished - Jan 2011


  • C and N availability
  • C metabolism
  • Carbon
  • Soil microbial biomass
  • Stable isotopes

ASJC Scopus subject areas

  • Microbiology
  • Soil Science


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