Simultaneous Remediation and Detection of Bioavailable Soil Cadmium Using Recombinant Rhizosphere Bacteria

EPA Grant Number: MA916348
Title: Simultaneous Remediation and Detection of Bioavailable Soil Cadmium Using Recombinant Rhizosphere Bacteria
Investigators: Wu, Cindy
Institution: University of California - Riverside
EPA Project Officer: Zambrana, Jose
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $86,444
RFA: GRO Fellowships for Graduate Environmental Study (2004) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Engineering


The goal of this research project is to investigate the feasibility of rhizoremediation and the use of bacterial biosensor to detect bioavailable cadmium. The specific objectives of this research are to: (1) investigate the feasibility of using a rhizosphere bacterium expressing synthetic phytochelatin as bacterial biosorbent for the cleanup of cadmium; (2) develop a bacterial biosensor, using the cadR promoter and a reporter gene, to detect bioavailable soil cadmium; and (3) construct a dual function microbial community system utilizing recombinant rhizosphere bacteria to remediate and detect soil cadmium in situ.


Cadmium is a metallic element that is persistent in the environment and extremely toxic to most organisms; therefore, a cost-effective and efficient remediation method is needed. The first aim of this research is to combine biosorption and rhizosphere remediation technologies to cleanup cadmium contaminated soil in situ. Rhizoremediation is the use of the root-bacteria symbiosis to cleanup contaminants. A synthetic phytochelatin will be expressed in the rhizosphere bacterium Pseudomonas putida to enhance its cadmium-binding capacity. Cadmium-binding experiments in the rhizosphere will be performed to evaluate the effectiveness of rhizoremediation in removing soil cadmium. The second aim is to apply genetic molecular methods to develop a bacterial biosensor capable of distinguishing between potentially nonhazardous and hazardous soil cadmium and to provide a monitoring tool for the rhizoremediation progress. The naturally occurring cadmium resistant metalloregulatory cadR promoter, found in P. putida, and the green fluorescent protein will be utilized in the construction of the nanoscale, highly specific cadmium (II) biosensor. A calibration curve of cadmium concentration and the fluorescence intensity will be generated. The environmentally robust P. putida is suitable for field applications. The cadmium biosensor has the potential to improve risk assessment techniques and impact policies regarding risk-based remedial planning. The third aim is to establish a novel, self-sustainable recombinant bacterial community by introducing the two recombinant strains of bacteria into the rhizosphere. The dual function microbial population in the rhizosphere will be capable of simultaneous cleaning and monitoring of bioavailable soil cadmium in situ.

Supplemental Keywords:

fellowship, cadR promoter, bioavailable cadmium, soil cadmium, Cd, bacterial biosensor, Pseudomonas putida, green fluorescent protein, recombinant bacteria,, Scientific Discipline, Waste, Water, POLLUTANTS/TOXICS, RESEARCH, Environmental Chemistry, Contaminated Sediments, Monitoring, Microbiology, Biochemistry, Soil Contaminants, Environmental Engineering, bioavailability, contaminated sediment, bio-engineering, biomonitoring, bioremediation of soils, remediation, recombinant rhizosphere bacteria, treatment, biosensors, cadmium, rhizososphere

Progress and Final Reports:

  • 2004
  • 2005
  • Final