HR: 0800h
AN: B11C-0625    [Abstracts]
TI: Diverse anaerobic Cr(VI) tolerant bacteria from Cr(VI)-contaminated 100H site at Hanford
AU: * Chakraborty, R
EM: RChakraborty@lbl.gov
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AU: Phan, R
EM: RPhan@lbl.gov
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AU: Lam, S
EM: benlam_8317@yahoo.com
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AU: Leung, C
EM: ambroseleungchinman@yahoo.com.hk
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AU: Brodie, E L
EM: ELBrodie@lbl.gov
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AU: Hazen, T C
EM: TCHazen@lbl.gov
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, 70A, Room 3317, Berkeley, CA 94720,
AB: Hexavalent Chromium [Cr(VI)] is a widespread contaminant found in soil, sediment, and ground water. Cr(VI) is more soluble, toxic, carcinogenic, and mutagenic compared to its reduced form Cr(III). In order to stimulate microbially mediated reduction of Cr(VI), a poly-lactate compound HRC was injected into the chromium contaminated aquifers at site 100H at Hanford. Based on the results of the bacterial community composition using high-density DNA microarray analysis of 16S rRNA gene products, we recently investigated the diversity of the dominant anaerobic culturable microbial population present at this site and their role in Cr(VI) reduction. Positive enrichments set up at 30°C using specific defined anaerobic media resulted in the isolation of an iron reducing isolate strain HAF, a sulfate reducing isolate strain HBLS and a nitrate reducing isolate, strain HLN among several others. Preliminary 16S rDNA sequence analysis identifies strain HAF as Geobacter metallireducens, strain HLN as Pseudomonas stutzeri and strain HBLS as a member of Desulfovibrio species. Strain HAF isolated with acetate as the electron donor utilized propionate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Growth was optimal at 37°C, pH of 6.5 and 0% salinity. Strain HLN isolated with lactate as electron donor utilized acetate, glycerol and pyruvate as alternative carbon sources, and reduced metals like Mn(IV) and Cr(VI). Optimal growth was observed at 37°C, at a pH of 7.5 and 0.3% salinity. Anaerobic active washed cell suspension of strain HLN reduced almost 95 micromolar Cr(VI) within 4 hours relative to controls. Further, with 100 micromolar Cr(VI) as the sole electron acceptor, cells of strain HLN grew to cell numbers of 4.05X 10⁷/ml over a period of 24hrs after an initial lag, demonstrating direct enzymatic Cr(VI) reduction by this species. 10mM lactate served as the sole electron donor. These results demonstrate that Cr(VI) immobilization at the Hanford 100H site could be mediated by direct microbial metabolism apart from indirect chemical reduction of Cr(VI) by end products of microbial activity.
DE: 0418 Bioremediation
DE: 0448 Geomicrobiology
SC: Biogeosciences [B]
MN: 2007 Fall Meeting