HR: 16:30h
AN: B24D-03    [Abstracts]
TI: Diversity and As-adsorption properties of Mn(II)-oxidizing bacteria within tropical wetlands of the Mekong Delta
AU: * Ying, S C
EM: samying@gmail.com
AF: Stanford University, Dept of GES 450 Serra Mall Bldg 320, Room 118, Stanford, CA 94305-2115, United States
AU: Kocar, B D
EM: kocar@stanford.edu
AF: Stanford University, Dept of GES 450 Serra Mall Bldg 320, Room 118, Stanford, CA 94305-2115, United States
AU: Fendorf, S
EM: fendorf@stanford.edu
AF: Stanford University, Dept of GES 450 Serra Mall Bldg 320, Room 118, Stanford, CA 94305-2115, United States
AU: Francis, C A
EM: caf@stanford.edu
AF: Stanford University, Dept of GES 450 Serra Mall Bldg 320, Room 118, Stanford, CA 94305-2115, United States
AB: Manganese (Mn) and iron (Fe) oxides are ubiquitous minerals that occur under similar redox conditions in terrestrial systems and have high sorptive capacities for many trace metals, including arsenic (As). In most natural environments, Fe oxidation is dominated by abiotic processes, while Mn oxides are primarily formed via bacterial Mn(II) oxidation, and both processes can profoundly impact the mobility of metal(loid) contaminants. Deciphering the mechanisms involved in arsenic transport within soils and sediments is essential for aiding many Southeast Asian countries, including Cambodia, where naturally occurring As is in groundwater at concentrations well above the WHO recommended limit. Although numerous past studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, it is unknown whether, in the presence of both oxides, there is preferential adsorption of As onto one oxide over the other. In the present study, we examine the competitive retention of As(III) and As(V) on goethite and biogenic Mn oxides using Donnan membranes--where each oxides is isolated by a semi-permeable membrane through which arsenic can migrate. Mn(II)-oxidizing bacteria, isolated from several Mn-rich sites along the Mekong River and wetland areas within the Mekong delta, were dominated by a diverse array of Bacillus strains that rapidly oxidize Mn(II) within three to five days in liquid culture. The results of this study not only expand our knowledge of the diversity and biogeochemical importance of terrestrial Mn(II)-oxidizing bacteria, but also contribute to our understanding the relative impact of Fe and Mn oxides on arsenic retention within natural wetlands.
DE: 0410 Biodiversity
DE: 0461 Metals
DE: 0463 Microbe/mineral interactions
DE: 0471 Oxidation/reduction reactions (4851)
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting