title: Simultaneous microbial reduction of iron(III) and arsenic(V) in suspensions of hydrous ferric oxide.
abstract: Bacterial reduction of arsenic(V) and iron(III) oxides influences the redox cycling and partitioning of arsenic (As) between solid and aqueous phases in sediment-porewater systems. Two types of anaerobic bacterial incubations were designed to probe the relative order of As(V) and Fe(III) oxide reduction and to measure the effect of adsorbed As species on the rate of iron reduction, using hydrous ferric oxide (HFO) as the iron substrate. In one set of experiments, HFO was pre-equilibrated with As(V) and inoculated with fresh sediment from Haiwee Reservoir (Olancha, CA), an As-impacted field site. The second set of incubations consisted of HFO (without As) and As(III)- and As(V)- equilibrated HFO incubated with Shewanella sp. ANA-3 wild-type (WT) and ANA-3deltaarrA, a mutant unable to produce the respiratory As(V) reductase. Of the two pathways for microbial As(V) reduction (respiration and detoxification), the respiratory pathway was dominant under these experimental conditions. In addition, As(III) adsorbed onto the surface of HFO enhanced the rate of microbial Fe(III) reduction. In the sediment and ANA-3 incubations, As(V) was reduced simultaneously or prior to Fe(III), consistent with thermodynamic calculations based on the chemical conditions of the ANA-3 WT incubations.
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology, Pasadena 91125, USA.
authors.forename: Kate M
authors.initials: KM
authors.lastname: Campbell
authors.forename: Davin
authors.initials: D
authors.lastname: Malasarn
authors.forename: Chad W
authors.initials: CW
authors.lastname: Saltikov
authors.forename: Dianne K
authors.initials: DK
authors.lastname: Newman
authors.forename: Janet G
authors.initials: JG
authors.lastname: Hering
mesh_terms: D000085:Acetates / Q000378:metabolism; D000327:Adsorption; D001151:Arsenic / Q000737:chemistry / Q000378:metabolism*; D002140:California; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism; D019015:Geologic Sediments / Q000382:microbiology*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D010084:Oxidation-Reduction; D020592:Shewanella / Q000235:genetics / Q000378:metabolism*; D014881:Water Supply
chemical_list: D000085:Acetates; D005290:Ferric Compounds; C000499:ferric oxide; D019344:Lactic Acid; D007501:Iron; D001151:Arsenic