title: Iodide accumulation by aerobic bacteria isolated from subsurface sediments of a 129I-contaminated aquifer at the Savannah River site, South Carolina.
abstract: (129)I is of major concern because of its mobility in the environment, excessive inventory, toxicity (it accumulates in the thyroid), and long half-life (∼16 million years). The aim of this study was to determine if bacteria from a (129)I-contaminated oxic aquifer at the F area of the U.S. Department of Energy's Savannah River Site, SC, could accumulate iodide at environmentally relevant concentrations (0.1 μM I(-)). Iodide accumulation capability was found in 3 out of 136 aerobic bacterial strains isolated from the F area that were closely related to Streptomyces/Kitasatospora spp., Bacillus mycoides, and Ralstonia/Cupriavidus spp. Two previously described iodide-accumulating marine strains, a Flexibacter aggregans strain and an Arenibacter troitsensis strain, accumulated 2 to 50% total iodide (0.1 μM), whereas the F-area strains accumulated just 0.2 to 2.0%. Iodide accumulation by FA-30 was stimulated by the addition of H(2)O(2), was not inhibited by chloride ions (27 mM), did not exhibit substrate saturation kinetics with regard to I(-) concentration (up to 10 μM I(-)), and increased at pH values of <6. Overall, the data indicate that I(-) accumulation likely results from electrophilic substitution of cellular organic molecules. This study demonstrates that readily culturable, aerobic bacteria of the F-area aquifer do not accumulate significant amounts of iodide; however, this mechanism may contribute to the long-term fate and transport of (129)I and to the biogeochemical cycling of iodine over geologic time.
authors.affiliation: Department of Marine Sciences, Texas A&M University, Galveston, Texas 77553, USA.
authors.forename: Hsiu-Ping
authors.initials: HP
authors.lastname: Li
authors.forename: Robin
authors.initials: R
authors.lastname: Brinkmeyer
authors.forename: Whitney L
authors.initials: WL
authors.lastname: Jones
authors.forename: Saijin
authors.initials: S
authors.lastname: Zhang
authors.forename: Chen
authors.initials: C
authors.lastname: Xu
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Schwehr
authors.forename: Peter H
authors.initials: PH
authors.lastname: Santschi
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Kaplan
authors.forename: Chris M
authors.initials: CM
authors.lastname: Yeager
mesh_terms: D001420:Bacteria, Aerobic / Q000378:metabolism*; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D007457:Iodine Radioisotopes / Q000032:analysis / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D045483:Rivers; D013022:South Carolina
chemical_list: D007457:Iodine Radioisotopes; D012336:RNA, Ribosomal, 16S