Call for Rhizosphere (Rhizo) Critical Campaign Proposals, FY 2027

The fiscal year 2026 Rhizosphere (Rhizo) Critical Campaign—a science-driven effort across the contiguous United States—is designed to advance basic understanding of microbial and biogeochemical processes that drive critical mineral (CM) recovery and uptake in plants via root-microbe-mineral interactions in the rhizosphere.

This call invites the community to submit samples targeting ultramafic sites (e.g., serpentinite soil) with preferably high (≥1,000 ppm) nickel (Ni) concentrations. While this campaign is mainly focused on Ni, associated critical minerals such as cobalt (Co) may be considered. Knowledge generated by this campaign will advance the Department of Energy (DOE) Office of Science's Biological and Environmental Research program's mission to develop critical mineral biomining technologies and feedstocks, whereas data will be released in EMSL's Science Central database as open FAIR, structured (AI-ready) data to support the Department of Energy's Genesis Mission.

Questions about the campaign? Please email Amir Ahkami, primary campaign contact.

Campaign Participants

Each campaign participant will receive a standardized suite of data from advanced, comprehensive sample analysis. View data types below.

Participants will contribute directly to achieving the community‑scale science objectives of the effort. Participants will have the opportunity to leverage the collective power of the research community and collaborate with the campaign leads and EMSL scientists to explore the complex biogeochemical processes governing critical mineral mobilization and uptake in the rhizosphere. All generated data from this campaign will be quality checked and made available to the public at no cost through EMSL's Science Central. Participants are encouraged to use these data in future peer‑reviewed publications to help maximize the scientific impact of the campaign.

Proposal Types

Participants should choose one of the proposal types listed below.

1. RhizoCosm: Controlled Microcosm Experiments               
    
   • Proposal Content. RhizoCosm proposals will focus on the function of known hyperaccumulator plant species in different ultramafic soils under controlled laboratory conditions. As part of these experiments, we will accept ultramafic soils from the scientific community and cultivate a model hyperaccumulator species and a non-hyperaccumulator species in growth chambers. Following plant growth, multiple sample types—including bulk soil (soil that is not directly associated with roots), rhizosphere soil (soil adhering to root), root tissue, and leaf tissue—will be collected in the laboratory for downstream analyses.               
      
   • Samples Requested: Bulk soil. A minimum of 30 kg of bulk soil should be collected and shipped in buckets. Additional soil may be needed to support follow‑up testing or to repeat experiments if required.     
      
2. RhizoField: In-Situ Field Sampling        
    
   • Sampling Focus. RhizoField proposals will focus on samples collected directly from vegetated ultramafic soil sites.     
      
   • Samples Requested: Bulk soil, rhizosphere soil (soil adhering to root), root tissue, and leaf tissue. Up to 20 samples per sample type (including biological replicates) may be submitted. Please email EMSL User Program Services in advance with any questions regarding sample sizes or acceptable sample types before submitting your proposal.     
      
   • Preferred Work. Preference will be given for known hyperaccumulators. Non-hyperaccumulators will be considered. Shrubs and grasses are preferred. Trees are excluded.     
      

Qualifying Criteria

Users will be required to submit supporting evidence (published data, geologic maps, and photographs) of high-Ni soil (≥1,000 ppm).

Proposal Submission and Review

Please follow these steps:

1. Read through the submission guide. (PDF) 
    
2. Download and complete the Rhizosphere Critical Request Form. (Word) 
    
3. Submit your proposal through the EMSL User Portal (NEXUS).

Initial technical review of proposals will be based on alignment with the campaign objectives and sample eligibility, as well as technical feasibility. Proposals that pass technical review will be prioritized for acceptance in the chronological order in which they are received (e.g., proposals received first that pass review will be awarded first).

Data Types

All samples will be subject to a suite of advanced and comprehensive analyses based on the proposal type.

About Rhizo Critical Campaign 

Campaign Leadership Team:

• Om Parkash Dhankher, University of Massachusetts Amherst
• Courtney Creamer, U.S. Geological Survey
• Erin Nuccio, Lawrence Livermore National Laboratory
• Jennifer Pett-Ridge, Lawrence Livermore National Laboratory

The basic mechanisms of how hyperaccumulator plant species take up critical minerals at root-soil interface are only partially understood. Specifically, key knowledge gaps include: (1) a limited mechanistic understanding of how microbes, root exudates, and minerals jointly drive Ni solubilization through coupled biomolecular and pore-scale geochemical processes; and (2) an incomplete understanding of the functional roles of rhizosphere microbial communities and their interactions with root exudates in controlling ion mobilization and uptake.

The overarching hypothesis of this campaign is that Ni mobilization and plant uptake in ultramafic systems are governed primarily by coupled rhizosphere processes—root exudation profiles that restructure microbial community composition and function and shift pore-scale geochemistry—thereby driving the soil into a distinct, biogeochemical state with higher bioavailable Ni than nearby non-rhizosphere soils. Addressing these gaps and hypotheses requires targeted sampling of field sites with ultramafic or metal-rich soils.

The research is organized around three key thrusts:

1. Mechanistic rhizosphere biogeochemistry for Ni mobilization and plant uptake in ultramafic soils. Develop a mechanistic understanding of coupled biomolecular and pore-/nano-scale geochemical processes—microbe–root exudate–mineral interactions controlling mineral dissolution, metal complexation, and redox—governing Ni solubilization and uptake under relevant field conditions, including contrasts between bulk soil and rhizosphere soil.
    
2. Functional microbiome–metabolite controls on ion mobilization, selectivity, and co-mobilization trade-offs in hyperaccumulators vs. non-hyperaccumulators. Determine the functional roles of rhizosphere microbial communities and their interactions with rhizosphere metabolites including root exudates in regulating ion mobilization and selectivity, as well as whether microbial contributions to metal uptake are constitutive or induced by plant signaling, and how these processes vary across seasonal and spatial gradients.             
    
3. Integrated field-to-lab workflows with shared data resources and predictive modeling. Establish field–laboratory experimental designs (pairing model hyperaccumulator systems with ultramafic field surveys), supported by collaborative data-sharing platforms and advanced numerical biogeochemical models to produce scalable, reproducible, AI-ready datasets that inform optimization of critical mineral uptake. 

Overall, the Rhizo Critical Campaign will investigate how hyperaccumulator plants (or plants with potential for phytoextraction of CMs) and their associated microbiomes can be leveraged for phytomining, thus generating insights into the biological processes that drive critical mineral uptake. Building on this foundation, this campaign aims to establish a sustainable, bio‑based framework for future mineral recovery strategies.

Questions About the Campaign?

Please email Amir Ahkami, primary campaign contact.