title: Multispecies Biofilms Transform Selenium Oxyanions into Elemental Selenium Particles: Studies Using Combined Synchrotron X-ray Fluorescence Imaging and Scanning Transmission X-ray Microscopy.
abstract: Selenium (Se) is an element of growing environmental concern, because low aqueous concentrations can lead to biomagnification through the aquatic food web. Biofilms, naturally occurring microbial consortia, play numerous important roles in the environment, especially in biogeochemical cycling of toxic elements in aquatic systems. The complexity of naturally forming multispecies biofilms presents challenges for characterization because conventional microscopic techniques require chemical and physical modifications of the sample. Here, multispecies biofilms biotransforming selenium oxyanions were characterized using X-ray fluorescence imaging (XFI) and scanning transmission X-ray microscopy (STXM). These complementary synchrotron techniques required minimal sample preparation and were applied correlatively to the same biofilm areas. Sub-micrometer XFI showed distributions of Se and endogenous metals, while Se K-edge X-ray absorption spectroscopy indicated the presence of elemental Se (Se0). Nanoscale carbon K-edge STXM revealed the distributions of microbial cells, extracellular polymeric substances (EPS), and lipids using the protein, saccharide, and lipid signatures, respectively, together with highly localized Se0using the Se LIIIedge. Transmission electron microscopy showed the electron-dense particle diameter to be 50-700 nm, suggesting Se0nanoparticles. The intimate association of Se0particles with protein and polysaccharide biofilm components has implications for the bioavailability of selenium in the environment.
authors.forename: Soo In
authors.initials: SI
authors.lastname: Yang
authors.forename: Graham N
authors.initials: GN
authors.lastname: George
authors.affiliation: National Hydrology Research Centre, Environment Canada , Saskatoon, Saskatchewan S7N 3H5, Canada.
authors.forename: John R
authors.initials: JR
authors.lastname: Lawrence
authors.forename: Susan G W
authors.initials: SG
authors.lastname: Kaminskyj
authors.affiliation: Canadian Light Source , Saskatoon, Saskatchewan S7N 2V3, Canada.
authors.forename: James J
authors.initials: JJ
authors.lastname: Dynes
authors.affiliation: Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Barry
authors.initials: B
authors.lastname: Lai
authors.forename: Ingrid J
authors.initials: IJ
authors.lastname: Pickering
mesh_terms: D018441:Biofilms; D008853:Microscopy; D012643:Selenium / Q000378:metabolism*; D017356:Synchrotrons; D014965:X-Rays
chemical_list: D012643:Selenium