title: Correlative Cryogenic Spectromicroscopy to Investigate Selenium Bioreduction Products.
abstract: Accurate mapping of the composition and structure of minerals and associated biological materials is critical in geomicrobiology and environmental research. Here, we have developed an apparatus that allows the correlation of cryogenic transmission electron microscopy (cryo-TEM) and synchrotron hard X-ray microprobe (SHXM) data sets to precisely determine the distribution, valence state, and structure of selenium in biofilms sampled from a contaminated aquifer near Rifle, CO. Results were replicated in the laboratory via anaerobic selenate-reducing enrichment cultures. 16S rRNA analyses of field-derived biofilm indicated the dominance of Betaproteobacteria from the Comamonadaceae family and uncultivated members of the Simplicispira genus. The major product in field and culture-derived biofilms is ∼25-300 nm red amorphous Se0aggregates of colloidal nanoparticles. Correlative analyses of the cultures provided direct evidence for the microbial dissimilatory reduction of Se(VI) to Se(IV) to Se0. Extended X-ray absorption fine-structure spectroscopy showed red amorphous Se0with a first shell Se-Se interatomic distance of 2.339 ± 0.003 Å. Complementary scanning transmission X-ray microscopy revealed that these aggregates are strongly associated with a protein-rich biofilm matrix. These findings have important implications for predicting the stability and mobility of Se bioremediation products and understanding of Se biogeochemical cycling. The approach, involving the correlation of cryo-SHXM and cryo-TEM data sets from the same specimen area, is broadly applicable to biological and environmental samples.
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Sirine C
authors.initials: SC
authors.lastname: Fakra
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Birgit
authors.initials: B
authors.lastname: Luef
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Cindy J
authors.initials: CJ
authors.lastname: Castelle
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Mullin
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Williams
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Marcus
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Denise
authors.initials: D
authors.lastname: Schichnes
authors.affiliation: Department of Earth and Planetary Science and ‡Department of Plant & Microbial Biology, University of California , Berkeley, California 94720, United States.|Advanced Light Source and ∥Earth Sciences Division, Lawrence Berkeley National Lab , Berkeley, California 94720, United States.
authors.forename: Jillian F
authors.initials: JF
authors.lastname: Banfield
mesh_terms: D001673:Biodegradation, Environmental; D060587:Groundwater; D012336:RNA, Ribosomal, 16S; D064586:Selenic Acid; D012643:Selenium
chemical_list: D012336:RNA, Ribosomal, 16S; D012643:Selenium; D064586:Selenic Acid