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In situ characterization of associations and resource exchange between free-living nitrogen-fixers and switchgrass


EMSL Project ID
50682

Abstract

This project will increase our understanding of carbon (C) and nitrogen (N) exchange in the rhizosphere. Specifically, we aim to understand how free-living nitrogen-fixing bacteria (diazotrophs) may provide N to bioenergy crops, such as switchgrass (Panicum virgatum), in exchange for root exuded C. The process by which atmospheric N2 is converted into ammonia by bacteria is energetically expensive. Diazotrophs living in the rhizosphere (root surface and associated soil) of bioenergy crops, such as switchgrass, perform free-living nitrogen-fixation (FLNF) and are very likely important supporters of productivity, particularly in N-limited systems such as marginal lands (Ruan et al. 2016). In exchange for fixed N, switchgrass is thought to provide energy-hungry diazotrophs with C via root exudation. Yet, direct evidence for FLNF in switchgrass rhizospheres and for the direct exchange of root exudate C for fixed N is lacking. Using a unique combination of state-of-the-art instruments and methods, we will help fill these knowledge gaps as we address the following questions: Where and how do diazotrophs associate with switchgrass roots? Do diazotrophs exchange fixed N for exuded C and what are the mechanisms behind this exchange? How does root exudate chemistry impact switchgrass-diazotroph interactions?

Project Details

Start Date
2019-01-11
End Date
2020-03-20
Status
Closed

Team

Principal Investigator

Kirsten Hofmockel
Institution
Pacific Northwest National Laboratory

Team Members

Darian Smercina
Institution
Kula Bio, Inc.

Maren Friesen
Institution
Washington State University

Sarah Evans
Institution
Michigan State University

Lisa Tiemann
Institution
Michigan State University