Mapping Soil Carbon from Cradle to Grave: ‘Omic and Isotope Based Measurements of Root C Transformations

Wednesday, 17 December 2014: 9:00 AM
Jennifer Pett-Ridge1, Erin E Nuccio1,2, Shengjing Shi2, Rachel Neurath1,2, Eoin Brodie3, Jizhong Zhou4, Mary Suzanne Lipton5, Donald Herman2 and Mary Firestone2, (1)Lawrence Livermore National Laboratory, Chemical Sciences Division, Livermore, CA, United States, (2)University of California Berkeley, Berkeley, CA, United States, (3)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (4)University of Oklahoma Norman Campus, Norman, OK, United States, (5)Pacific Northwest National Laboratory, Richland, WA, United States
Carbon cycling in the rhizosphere is a nexus of biophysical interactions between plant roots, microorganisms, and the soil organo-mineral matrix. Plant roots are the primary inputs of soil organic C; the presence of roots significantly alters rates of organic matter mineralization by soil microbes. Our research on how roots influence decomposition of soil organic matter in both simplified and complex microcosms uses geochemical characterization, molecular microbiology, isotope tracing, ‘omics and novel imaging approaches (‘ChipSIP’ and ‘STXM-SIMS’) to trace the fate of isotopically labelled root exudates and plant tissues. Our work seeks to understand the genomic basis for how organic C transformation and decomposition in soil is altered by interactions between plant roots and the soil microbial community (bacteria, archaea, fungi, microfauna). We hypothesize that root-exudate stimulation of soil microbial populations results in the altered expression of transcripts and proteins involved in decomposition of macromolecular C compounds. Using an isotope array that allows us to follow root C into bacterial, fungal, and microfaunal communities, we have tracked movement of 13C from labeled exudates and 15N from labeled root litter into the soil microbial community, and linked this data to 16S profiles and community gene transcripts. By integrating stable isotopes as tracers of natural resource utilization (i.e. root litter), and analysis of the functional properties of the communities that respond to those resources, we can identify the molecular pathways that are stimulated in the soil microbiome in response to root litter, living roots, and their interfaces.