title: Electron energy loss spectroscopy techniques for the study of microbial chromium(VI) reduction.
abstract: Electron energy loss spectroscopy (EELS) techniques were used to determine oxidation state, at high spatial resolution, of chromium associated with the metal-reducing bacteria, Shewanella oneidensis, in anaerobic cultures containing Cr(VI)O4(2-). These techniques were applied to fixed cells examined in thin section by conventional transmission electron microscopy (TEM) as well as unfixed, hydrated bacteria examined by environmental cell (EC)-TEM. Two distinct populations of bacteria were observed by TEM: bacteria exhibiting low image contrast and bacteria exhibiting high contrast in their cell membrane (or boundary) structure which was often encrusted with high-contrast precipitates. 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.
authors.affiliation: Marine Geosciences Division, Naval Research Laboratory, Stennis Space Center, MS 39529, USA. tld@howdy.wustl.edu
authors.forename: Tyrone L
authors.initials: TL
authors.lastname: Daulton
authors.forename: Brenda J
authors.initials: BJ
authors.lastname: Little
authors.forename: Kristine
authors.initials: K
authors.lastname: Lowe
authors.forename: Joanne
authors.initials: J
authors.lastname: Jones-Meehan
mesh_terms: D002857:Chromium / Q000737:chemistry*; D003470:Culture Media; D008854:Microscopy, Electron / Q000295:instrumentation / Q000379:methods*; D020592:Shewanella / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure*; D013057:Spectrum Analysis / Q000295:instrumentation / Q000379:methods*
chemical_list: D003470:Culture Media; D002857:Chromium; C074702:chromium hexavalent ion