Soil Microbial Mechanisms Controlling Trace Metal Bioavailability and Transport

EPA Grant Number: F07F10964
Title: Soil Microbial Mechanisms Controlling Trace Metal Bioavailability and Transport
Investigators: Sullivan, Tarah S.
Institution: Cornell University
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 2007 through September 1, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Fellowship - Soil Microbiology , Academic Fellowships


Heavy metal contamination of soils poses significant hazard to human, plant, and animal health in addition to reducing or eliminating the functional capacity of a given ecosystem. In many soil environments, trace metals exist in recalcitrant forms, not readily available for plant uptake and not conducive to bioremediation or phytoextraction techniques. Therefore bioavailability of heavy metals in the soil is one of the primary limitations to effective phytoremediation.

This research will explore two dominant microbial mechanisms involved in controlling trace metal bioavailability in soils and attempt to achieve an understanding of the relative contribution of each microbial mechanism to plant metal uptake: microbial siderophore biosynthesis, and microbial metal-sulfide oxidation.


Soil microbial communities will be sampled from ecosystems where heavy metal levels are inherently high but relatively unavailable, thereby resulting in populations of microorganisms adapted to recalcitrant heavy-metal acquisition. I will use classical culturing methods to screen for microbial production of siderophores and microbial capacity to oxidize sulfur-metal complexes, as well as molecular methods to assess genetic capacity to perform these functions by targeting specific functional genes involved in each process.

Following the microbial identification and characterization, I will also conduct a set of greenhouse growth-chamber experiments utilizing various seedlings and cuttings of plant species often used in metal phytoremediation to determine metal uptake and accumulation response to various microbial isolates and consortia obtained from the field. Combining multiple different techniques allows a crucial multidisciplinary approach to the question of how important these microbial mechanisms are in metal availability and plant uptake.

Expected Results:

The design of my research allows unique and vital understanding of the importance of multiple microbial processes, and the relative contribution of each, to plant metal uptake. I intend for my research to, first and foremost, expand the current scientific understanding of rhizosphere interactions and to begin to fill the knowledge gaps with regard to plant metal uptake, but also to serve as a launching point for further research on inocula production of the organisms and consortia important for plant metal uptake and phytoextraction.

Supplemental Keywords:

soil microbial community, heavy metal contamination, remediation, phytoremediation, phytoextraction, siderophores, sulfur oxidation, terrestrial systems ecology, sulfide, environmental metal toxicology, hyperaccumulation, rhizosphere interactions, bioleaching, metal tolerance, microbial metal adaptations,

Progress and Final Reports:

  • 2008
  • 2009
  • Final