State Water Resources Research Institute Program

Project ID: 2008OH65B
Title: Bioremediation of heavy metals using the genetically engineered bacterium Caulobacter crescentus
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: OH-005
Focus Categories: Treatment, Toxic Substances, Water Quality
Keywords: heavy metals, bioremediation, genetic engineering
Principal Investigators: Xu, Zhaohui (Bowling Green State University); McKay, Robert M (Bowling Green State University)
Federal Funds: $ 25,000
Non-Federal Matching Funds: $ 52,970
Abstract: PROBLEM: Water contaminated by heavy metals poses a great danger to humans and the environment. Lake Erie provides drinking water for millions of Ohio residents living within its watershed. However, four Ohio coastal areas have been designated as Areas of Concern, at least partly, due to elevated levels of heavy metals, which contributes to impaired beneficial use of these areas, including "restrictions on drinking water consumption, or taste and odor". The Maumee River is identified as one of the most contaminated tributaries associated with Lake Erie. "It is the policy of the State of Oho to coordinate the development and implementation of Remedial Action Plans for Ohio's four Lake Erie Basin Areas of Concern as identified in the International Joint Commission's reports on Great Lakes water quality".

OBJECTIVE: We aim to develop a novel technology for cost-effective removal of heavy metals from contaminated water systems using genetically engineered Caulobacter crescentus strains. The bacterium is ubiquitous in our environment and is also endemic to Lake Erie. Bearing the strongest known biological adhesive on its stalk-like polar appendage, Caulobacter cells can attach themselves to a solid substrate, coating the substrate as a single layer biofilm. When heavy metal-binding peptides are incorporated onto the cell surface, the engineered strains can be readily immobilized on designed remediation bioreactors for safe retrieval of heavy metals. Given the fact that Caulobacter is completely safe to humans and the environment, the developed technology can potentially be applied to treatment processes involving drinking water, remediation of natural water bodies (such as Lake Erie and the Maumee River), and industrial wastewater.

METHODS: In this study, we will use recombinant DNA techniques to incorporate heavy metal-binding peptides into the Caulobacter S-layer protein RsaA. Bioaccumulation of heavy metals (for example, Cd2+) using these engineered strains will be investigated with a variety of water systems, such as drinking water spiked with individual or mixed heavy metals, industrial wastewater, as well as environmental samples collected from several locations in the Areas of Concern associated with Lake Erie.

Display of heavy metal-binding peptides on the Caulobacter cell surface. Through genetic manipulations, we will insert heavy metal-binding peptides (such as polyhistidine) to the permissive sites of RsaA. E. coli strains will be used as host cells for recombinant DNA manipulation, and Caulobacter strains will be used to express RsaA fusion proteins.

Bioaccumulation of heavy metals using engineered bacterial strains. Genetically engineered Caulobacter strains will be evaluated for their capacity to sequester heavy metals from different samples. Metal contents in the sample solutions before and after the treatment will be measured by ICP-OES (Induced Coupled Plasma-Optical Emission Spectrometer). The bioaccumulation capacity of each engineered strain will be determined and their field deployment prospects will be assessed.

Progress/Completion Report, PDF

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