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Evgenya S. Shelobolina, Sara A. Sullivan, Kathleen R. O'Neill, Kelly P. Nevin, and Derek R. Lovley

Isolation, Characterization, and U(VI)-Reducing Potential of a Facultatively Anaerobic, Acid-Resistant Bacterium from Low-pH, Nitrate- and U(VI)-Contaminated Subsurface Sediment and Description of Salmonella subterranea sp. nov.

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Evgenya S. Shelobolina, Sara A. Sullivan, Kathleen R. O'Neill, Kelly P. Nevin, and Derek R. Lovley

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  1. Isolation, Characterization, and U(VI)-Reducing Potential of a Facultatively Anaerobic, Acid-Resistant Bacterium from Low-pH, Nitrate- and U(VI)-Contaminated Subsurface Sediment and Description of Salmonella subterranea sp. nov. Evgenya S. Shelobolina, Sara A. Sullivan, Kathleen R. O'Neill, Kelly P. Nevin, and Derek R. Lovley 老師：李重義 學生：黃柏勝

  2. 前人研究 • Microbial reduction of soluble hexavalent uranium U(VI) to tetravalent uranium U(IV), which precipitates as the mineral uraninite, has been proposed as one of the methods for uranium immobilization • Two major groups of microorganisms reported to reduce U(VI) at a near-neutral pH are dissimilatory Fe(III)-reducing microorganisms and sulfate-reducing microorganisms.

  3. 前人研究 • In studies in which dissimilatory metal reduction was stimulated in sediments at a near-neutral pH, molecular analysis revealed that indigenous Fe(III)-reducing bacteria belonging to the Geobacteraceae family predominated during uranium reduction .

  4. 實驗方法 • 採樣 • 培養 • 分離 • 最適生長條件測定 • 生化特性測定 • 16s rRNA gene 鑑定

  5. 採樣 • Sediment was collected from the saturated zone of a low-pH area of the aquifer at site FW-024 at the NABIR Field Research Center in Oak Ridge, Tenn. • Sediment was collected on 3 April 2001 from horizons A1 to C1 below the water table

  6. 培養基 • NH4Cl (0.25 g/liter), • NaH2PO4 · H2O (4.2 g/liter), • KH2PO4 (0.18 g/liter) • vitamin solution (10 ml/liter) • mineral solution (10 ml/liter)

  7. 培養法 • Low-pH anaerobic enrichments were initiated in 27-ml pressure tubes containing 9 ml of modified freshwater (MFW) medium and 0.5 g of the sediment. • Nine milliliters of MFW medium was dispensed into each 27-ml anaerobic pressure tube and bubbled with N2. • A reducing agent (cysteine or FeCl2 at 0.5 or 0.7 mM, respectively) was added after the medium was autoclaved. • All cultures were incubated at 30°C. • Strain FRCl was enriched with H2 as the electron donor, acetate (10 mM) as the carbon source, and KNO3 (5 mM) as the electron acceptor. • After 1 month, the culture was serially diluted with the same anaerobic medium.

  8. 篩選策略 • 目標：希望能找到耐酸且為兼性厭養的鈾還原菌 • 在前人研究中發現，主要能夠還原鈾離子的是dissimilatory Fe(III)-reducing microorganisms and sulfate-reducing microorganisms，還原鈾的過程與能量獲得無關，可能是一種共代謝的過程 • 能夠還原鈾的微生物必須有抗鈾的能力 • 在受到鈾污染，成酸性環境的地方篩菌 • 在酸性無氧的環境下培養，篩Fe(III)-reducing microorganisms and sulfate-reducing microorganisms • 測定篩到的微生物是否有還原鈾的能力

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