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Michigan State University

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Superfund Research Program

Reductive Processes for Bioremediation of Chlorinated Solvent-Metal Mixtures

Project Leader: Craig S. Criddle (Stanford University)
Grant Number: P42ES004911
Funding Period: 2000 - 2006

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Project Summary (2000-2006)

This project is investigating the hypothesis that electron transport can be engineered for simultaneous and efficient metal reduction and dechlorination. Researchers have three specific objectives: 1) utilize biologically generated redox-active agents, including secreted factors, humic acids, and iron sulfide minerals, to construct electron transport chains that permit efficient transfer of electrons for reduction of metals and dechlorination; 2) characterize and engineer a model bacterium, Shewanella putrefaciens MR-1, that can improve electron flow for dechlorination and metal reduction; and 3) evalulate the organisms and electron transfer processes in aquifer sediment microcosms as well as the ecological effects of these processes.

The first specific objective is being addressed by screening model organisms and enrichments grown on insoluble electron acceptors or nutrients, by isolating bacteria capable of simultaneous dechlorination and metal reduction, and by cultivating organisms capable of generating FeS (iron sulfide) minerals. To investigate the second objective, researchers are monitoring the expression of genes required for electron transport and comparing to rates of dechlorination and metal reduction for varied concentrations and combinations of chlorinated solvents, chromate, secreted factors, and humic substances. Finally, dechlorination and metal reduction will be assayed for aquifer sediment microcosms treated using processes developed in the first two specific objectives. Changes in community structure will be monitored by quantitative PCR, by community genome arrays, and by analysis of 16S rDNA fragments.

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