| DOI: | 10.2172/1016122
|
| 报告号: | DOE/ER64372-1
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| 报告题名: | Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report |
| 作者: | Joel E. Kostka; Lee Kerkhof; Kuk-Jeong Chin; Martin Keller; Joseph W. Stucki
|
| 出版年: | 2011
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| 发表日期: | 2011-06-15
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| 国家: | 美国
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| 语种: | 英语
|
| 英文关键词: | nitrate reduction
; chromate reduction
; Geobacter metallireducens
; Desulfovibrio desulfuricans
; Sulfurospirillum barnesii
; nitrite reductase
; desulfoviridin
; multi-heme cyctochrome C
; proteomics
; MALDI-TOF
; LC/MS-MS
|
| 中文主题词: | 高温
; 氨
; 硝酸盐
; 亚硝酸盐
; 放射性核素
; 铁
; 金属
|
| 主题词: | HEAT
; AMMONIA
; NITRATE
; NITRITE
; RADIONUCLIDES
; IRON
; METALS
|
| 英文摘要: | A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory proteins (Gmet_2478 and Gmet_1641) were up-regulated with exposure to Cr(VI). A nine-heme cytochrome C was purified that could reduce nitrite and could be oxidized by Cr(VI). For D. desulfuricans, we found that confirmed that Cr(VI) induced a prolonged lag period when Cr(VI) was reduced. Over three hundred proteins were unequivocally identified by LC/MS-MS and a significant number of down-regulated proteins for which the levels were changed >2 fold compared to control. Sulfite reductase levels were similar, however, nitrate and nitrite reductase were down-regulated. The supernatant of spent cultures was found to contain a filterable, heat stable compound that rapidly reduced Cr(VI). In addition, desulfoviridin was purified from nitrate grown cells and shown to have nitrite reductase activity that was inhibited by Cr(VI). For S. barnesii, periplasmic nitrate reductase (Nap), nitrite reductase (Nrf), and the metalloid reductase (Rar) were purified and characterized. The supernatant of spent cultures was also found to contain a filterable, heat stable compound that rapidly reduced Cr(VI) but that Rar also reduced Cr(VI). Our results from specific aims 1 through 3 indicate that for G. metallireducens, Cr(VI) inhibits nitrate respiration as it oxidizes cytochromes involved in nitrate respiration. Iron reduction is apparently not affected and the inhibitory affects of Cr(VI) may be attenuated by the addition of sufficient Fe(III) to generate Fe(II) that abiotically reduces the chromium. For S. barnesii, although the enzyme assays indicate that the components of the respiratory pathway for nitrate (e.g. Nap and Nrf) are inhibited by chromate, the organism has a mechanism to prevent this from actually occurring. Our current hypothesis is that the non-specific metalloid reductase (Rar) is providing resistance by reducing the Cr(VI). The strategy here would be to enhance its growth and metabolism in the natural setting. Lactate is a suitable electron donor for S. barnesii but other donors are possible. Although the version of the Phylochip used for monitoring the microbial community at the Hanford site did not include S. barnesii it did have probes for detecting other Sulfurospirillum species (e.g., S. multivorans, S. halorespirans). For D. desulfuricans, again, redox active proteins such as dissimilatory nitrite reductase and dissimilary sulfite reductase are effectively oxidized by Cr(VI) thus inhibiting their reductive potential. More physiological and biochemical data are needed before a possible strategy can be designed and assessed. |
| URL: | http://www.osti.gov/scitech/servlets/purl/1016122
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| Citation statistics: |
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| 资源类型: | 研究报告
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/40197
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| Appears in Collections: | 过去全球变化的重建
影响、适应和脆弱性
科学计划与规划
气候变化与战略
全球变化的国际研究计划
气候减缓与适应
气候变化事实与影响
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| Recommended Citation: | |
Joel E. Kostka,Lee Kerkhof,Kuk-Jeong Chin,et al. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report. 2011-01-01.
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