Quantitative Environmental Cell - Transmission Electron Microscopy: Studies of Microbial Cr(VI) and Fe(III) Reduction
Abstract
Several applications of environmental cell (EC)-transmission electron microscopy (TEM) to microbial metal reduction studies are reviewed. Electron energy loss spectroscopy (EELS) techniques were used to determine oxidation state, at high spatial resolution, of Cr associated with the metal-reducing bacteria, Shewanella oneidensis, in anaerobic cultures containing Cr(VI)C >42-. These techniques were applied to fixed cells examined in thin section by conventional TEM and unfixed, hydrated bacteria examined by EC- TEM. Measurements by EELS demonstrated that cell boundaries became saturated with low concentrations of Cr and the precipitates encrusting bacterial cells contained a reduced form of Cr in oxidation state +3 or lower. In addition, reduction by S. oneidensis of structural Fe(lll) in nontronite, an expandable clay, was studied under anaerobic conditions. Direct observations by EC-TEM yield unambiguous measurement of layer spacings and the contraction of hydrated, clay layers upon reduction of structural Fe(lll). In particular, nonreduced and Fe(l Unreduced nontronite, observed by EC-TEM, exhibit mean (001) spacings 0 1.50 nm and 1.26 nm, respectively.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2002
- Accession Number
- ADA419541
Entities
People
- Brenda J. Little
- Jin Kim
- Kristine Lowe
- Steven Newell
- Tyron Daulton
Organizations
- United States Naval Research Laboratory