Cryo-EM investigations of interfacial bacterial extracellular polymeric substance (EPS) in vanadium interactions
EMSL Project ID
19828
Abstract
In anaerobic conditions, dissimilatory metal-reducing bacteria such as Shewanella oneidensis MR-1 can reduce a variety of polyvalent metal ions either as soluble complexes or associated with solid phase minerals. One such metal, vanadium, is a prevalent non-radioactive contaminant in groundwaters impacted by mining activities and at some Department of Energy sites. While oxidized V(V) presents significant health hazard, vanadium toxicity and solubility decrease as its valence state is reduced. Given the ability of S. oneidensis MR-1 to reduce V(V) (vanadate ion) to V(IV) (vanadyl ion) bioremediation can be used as an effective means for immobilizing this metal. The biotransformation of V(V) pentoxide (V2O5) to V(IV) by S. oneidensis MR-1 yields a granular, poorly-soluble precipitate which may be an effective remediation strategy for vanadium-contaminated groundwater. Similar to other metals and radionuclides, the reduction of V(V) has been linked to c-type cytochromes, particularly those associated with the outer membrane (OM) allowing contact with both extracellular soluble and insoluble electron acceptors. In some Gram-negative bacteria, extracellular polymeric substance (EPS) has been shown to have a significant metal binding capacity. Thus, the interactions of bacterial EPS with a reduced metal oxide could be advantageous to limiting subsequent reactivity or colloidal transport in a subsurface environment. Recently, we have shown the interaction of biogenically formed uraninite (UO2(s)) with an EPS produced by S. oneidensis MR-1. This UO2-EPS matrix was found to contain OM-associated cytochromes, integral OM protein and polysaccharide. Additional studies have shown that EPS production was a natural phenomena associated with the normal cell cycle of S. oneidensis and not an artifact of incubation with uranium. In fact, preliminary studies demonstrate that EPS production occurs in S. oneidensis MR-1 cells incubated with V(V). Together, this suggests that a through understanding of the interfacial interactions of bacterial EPS production with a non-radioactive metal contaminant, such as vanadium, could serve as a mechanistic model for understanding and predicting the long-term fate and transport of radionuclide contaminants in the subsurface.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2006-07-28
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Marshall MJ, Dohnalkova AC, Kennedy DW, Plymale AE, Thomas SH, Löffler FE, Sanford RA, Zachara JM, Fredrickson JK, Beliaev AS. 2009. Electron donor-dependent radionuclide reduction and nanoparticle formation by Anaeromyxobacter dehalogenans strain 2CP-C. Environ Microbiol doi:10.1111/j.1462-2920.2008.01795.x