You are here:
MECHANISM(S) OF UPTAKE AND SEQUESTRATION OF LEAD AND OTHER HEAVY METALS BY PSEUDOMONAS AERUGINOSA CHL-004
Citation:
FELDHAKE, D. J. AND W. J. DAVIS-HOOVER. MECHANISM(S) OF UPTAKE AND SEQUESTRATION OF LEAD AND OTHER HEAVY METALS BY PSEUDOMONAS AERUGINOSA CHL-004. Presented at Fifth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, May 22 - 25, 2006.
Impact/Purpose:
to present information
Description:
Heavy metals in soils and sediments of anthropogenic origin are a major environmental concern, due to the significant health risks they pose and due to the difficulties encountered with their remediation. Diverse industries involved in energy production, pigment synthesis and the refining of crude oil have resulted in the release of heavy metals into large tracts of land and into many miles of sediments worldwide. Bioremediation of heavy metals using bacteria generally involves the binding of positively charged metal ions to negatively charged components of the bacterial cell wall or other extracellular polymers or proteins. Pseudomonas species are known to produce and excrete iron-scavenging siderophores which may also bind other metals, but siderophores bound to metals other than iron generally do not re-enter the bacterial cell. Pseudomonas aeruginosa CHL-004 is unique in it's ability to transport lead from the exterior environment and store lead complexed with phosphate as discrete intracellular inclusions. The intracellular accumulation of both cadmium and arsenic has also been observed, suggesting an unusual role for siderophores in CHL-004's intracellular accumulation of heavy metals. Previous laboratory-scale experiments have shown that Pseudomonas aeruginosa CHL-004 can reduce lead concentrations in soil, and that CHL-004 is resistant to cadmium and arsenic in addition to accumulating these heavy metals intracellularly. At the same time, PCR using primers targeted to metal resistance genes have not detected the most common genes involved in metal efflux. We are investigating the potential involvement of siderophores in CHL-004's resistance to heavy metals and ability to accumulate heavy metals intracellularly. Metal uptake experiments with quantitative assays of siderophore production will evaluate the induction of siderophores in the wild-type CHL-004. CHL-004 mutants which have lost resistance to heavy metals will also be evaluated to determine if there is a corresponding loss of siderophore production. Additional molecular analyses using PCR will be performed to identify the mechanisms and the genes involved in the uptake and sequestration of heavy metals by CHL-004. The identification of a bacterial mechanism to bioaccumulate heavy metals from the environment and to store the metals intracellularly in a less bioavailable form could prove very useful in the bioremediation of heavy metals in soil and sediment.