Spectroscopic Confirmation of Enzymatic Oxidation of Structural Fe(II) in Biotite by a Lithoautotrophic Fe(II)-oxidizing Bacterial Culture
EMSL Project ID
37794
Abstract
The key rationale for submission of this rapid access user proposal is that we are nearing closure on the novel discovery of the potential for enzymatic oxidation of Fe(II) in biotite (see below), and wish to obtain independent verification, by both bulk (Mossbauer) and surface sensitive (XPS) techniques, of microbial oxidation as soon as possible before submitting the paper.Recent studies in our laboratory have demonstrated that the neutral-pH lithoautotrophic nitrate-reducing, Fe(II)-oxidizing enrichment culture described by Straub et al. (1996) (Appl. Environ. Microbiol., 62:1458-1460) is capable of continuous growth with biotite as the sole energy source. Growth of the culture resulted in a decrease in the 0.5M HCl-extractable Fe(II) content of biotite suspensions, corresponding to oxidation of ca. 20% of the total Fe(II) content of the mineral. We request Mossbauer spectroscopic and X-ray photoelectron spectroscopic (XPS) analysis of only two samples: speciments of biotite prior to and following microbial oxidation. Both Mossbauer and XPS have been widely applied in studies of chemical oxidative weathering of biotite, and will provide independent proof of structural Fe(II) oxidation by the culture. Mossbauer spectroscopy will reveal changes in the bulk Fe(II) content of the mineral, whereas XPS will reveal changes in the oxidation state of Fe on the mineral surface.
This study will provide the first demonstration of direct microbial involvement in the initial step of biotite weathering (i.e. Fe(II) oxidation), and will make an important contribution to the overall understanding of the pathways and quantitative significance of microbial phyllosilicate redox transformations in nature. The study is directly relevant to the EMSL Geochemistry/Biogeochemistry and Subsurface Science theme, specifically in terms of the reactivity of minerals toward oxidation and reduction processes, and biogeochemical interactions at the microbe-mineral interface. Roden and Shelobolina are serving as external collaborators on the current PNNL-SFA program, and the successful completion of this work will set the stage for the application of our combined microbiological and spectroscopic techniques to analysis of microbial transformation of phyllosilicates in Hanford sediments.
Project Details
Project type
Limited Scope
Start Date
2009-09-21
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members