Understanding Carbon Use Efficiency in Soil Ecosystems Using Metabolomics, Lipidomics, Protein Digests and Metabolic Modeling
EMSL Project ID
60191
Abstract
The efficiency with which organic compounds are used to produce microbial biomass is an important variable in modeling soil C cycling. This efficiency, called C use efficiency or CUE, is often determined by measuring the incorporation of uniformly 13C-labeled substrates into microbial biomass. The measurement is described as determining the efficiency of anabolic and catabolic processes (including maintenance and overflow respiration) in soil ecosystems. However, the value of CUE is also affected by the loss of biosynthesis products through exudation, secretion, extracellular proteins production, and cell death. On the other hand, soil metabolic flux analysis uses the measurement of CO2 production from individual substrate C atoms and calculates the activity of the pathways of the central C metabolic network such as glycolysis, TCA cycle, and CUE based on the distribution of CO2 production across C atoms. This method is better suited to determine the efficiency of anabolic and catabolic processes in complex soil communities and the value of this eco-physiological CUE is independent of any C losses. Although the position-specific CO2 production per substrate C atom provides a first estimate of soil metabolism, more information is available when analyzing the position-specific 13C incorporation into biosynthesis products. We propose to make use of EMSL’s capabilities and experience to measure how C-atoms from glucose become incorporated into soluble compounds, proteins and phospholipid fatty acids. To develop this improved method of metabolic flux analysis in intact soil communities, we propose to evaluate two mass-spectrometry techniques to determine the 13C incorporation into the target compounds: LC/GC-MS and LC/GC-IRMS. This project aims to characterize metabolism and CUE of soil microbes in two highly dynamic conditions under which large changes in metabolism and CUE are expected: 1) a response to a rapid increase in substrate concentration in an agricultural soil, and 2) a recovery of active metabolism after drought in a Californian grassland soil.
This project aims to answer the following questions. 1) Which substrate concentration, incubation duration, and analytical method is most appropriate for 13C metabolic flux analysis in soil communities? 2) Which compounds are most informative and easiest to analyze in short and long-term incubations? 3) How can we use this information to produce more realistic metabolic representations of soil activity? And finally, 4) what metabolic changes in microbial energy metabolism and CUE occur during rapid changes in microbial activity in response to substrate availability and recovery from drought under in situ soil conditions?
We request support for the extraction and analysis of 112 metabolomes to characterize the position-specific 13C incorporation into small organic compounds, protein digests, and lipids.
Project Details
Project type
Exploratory Research
Start Date
2021-12-01
End Date
2022-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members