You are here:
A Pyoverdin Siderophore Produced By Pseudomonas aeruginosa CHL-004 Binds Lead And Other Heavy Metals - (Poster)
Citation:
FELDHAKE, D. J., R. J. GROSSER, AND W. J. DAVIS-HOOVER. A Pyoverdin Siderophore Produced By Pseudomonas aeruginosa CHL-004 Binds Lead And Other Heavy Metals - (Poster). Presented at Remediation Of Chlorinated And Recalcitrant Compounds. The Sixth International Conference, Monterey, CA, May 19 - 22, 2008.
Impact/Purpose:
To characterize pyoverdin, its interaction with CHL-004, and its heavy metal binding capabilities.
Description:
Heavy metal pollution in soils, sediments and wastewater poses a significant environmental and public health threat due to toxicity and the potential for bioaccumulation in both plant and animal tissues. Remediation of heavy metals in soils and sediments using solely physical or chemical methods is expensive and not always effective for low concentrations of metals. These problems have led to a focus on bioremediation technology research to immobilize heavy metals, reduce bioavailability, or convert metals to less toxic species. Previous laboratory studies of the heavy metal resistant isolate Pseudomonas aeruginosa CHL-004 obtained from soil near tailings from a lead mine determined that CHL-004 is resistant to some heavy metals including lead, arsenic and cadmium. TEM/EDS (Transmission Electron Microscopy/Electron Dispersive X-Ray Spectroscopy) of CHL-004 has shown that lead is transported from the exterior environment, complexed with phosphate, and stored as discrete cellular inclusions; CHL-004 also accumulates cadmium and arsenic intracellularly. Current studies indicate that CHL-004 produces a pyoverdin siderophore that binds lead and some other heavy metals, and may bind to the bacterial cell while complexed with lead. Pyoverdins are yellow-green fluorescent siderophores excreted extracellularly when Pseudomonas grow in low-iron environments. Pyoverdins vary greatly in the composition and length of amino acid chains which make up part of their structures; this variability contributes to pyoverdins of different bacteria having different binding affinities for different metals. Although pyoverdins may bind a number of metals, they have not been shown to contribute to the uptake of metals other than iron. Pyoverdin fluorescence is generally quenched when pyoverdins bind Fe3+ and other suitable metal ions. When using an excitation wavelength of 405 nm and with an emission wavelength peak of approximately 488 nm, the fluorescence of CHL-004's pyoverdin is quenched upon the addition of lead and some other heavy metals. In addition, when grown in a pyoverdin-inducing liquid culture medium containing lead, the yellow chromogenic compound co-precipitates with the cellular biomass during centrifugation. Although pyoverdin is produced by CHL-004 in this same medium without lead addition, it remains in the supernatant after centrifugation. Efforts are now focused on characterizing this pyoverdin, its interaction with CHL-004, and its heavy metal binding capabilities. Both CHL-004 and the pyoverdin produced by CHL-004 may be useful tools for the bioremediation of lead and other heavy metals from soils, sediments and wastewater, and results suggest that this pyoverdin has a role in CHL-004's uptake and accumulation of lead.