Effect of Low Concentrations of Arsenic on Microbial Iron Reduction

低浓度砷对微生物铁还原的影响

• 批准号: 1325098
• 负责人: Martial Taillefert
• 金额: $ 39万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1325098&HistoricalAwards=false
• 关键词: Effect; Low; Concentrations; Arsenic; Microbial

In natural environments, arsenite (As(III)) is not only more mobile but is also more toxic than arsenate (As(V)) or organoarsenic compounds. Despite a wealth of knowledge gained in the laboratory or aquatic systems displaying remarkably high concentrations of arsenic, little research has been conducted on the effects of low arsenic inputs to natural aquatic systems. Incubations with sediments from a Georgia river revealed that low ( 10 micro M) but increasing As(V) concentrations spurred increases in microbial iron reduction rates accompanied by the secondary recrystallization of Fe oxides. In this project, the mechanism by which low concentrations of arsenic affect anaerobic respiration on Fe oxides by iron-reducing bacteria will be determined. It is hypothesized that As(V) stimulates the energy generation process in iron-reducing bacteria by substitution of phosphate by arsenate during phosphorylation of ADP. This effect is postulated to result from the expression of phosphate transporters and their regulators by iron-reducing bacteria in phosphate-limiting conditions. Finally, the large impact of submicromolar As(V) concentrations on microbial Fe reduction in natural environments is hypothesized to result from a catalytic cycle whereby As(III) produced by microbial detoxification is rapidly recycled to As(V) via chemical oxidation by Mn(IV) oxides present ubiquitously in natural environments. A series of incubations with pure cultures of metal-reducing Shewanella was designed to investigate in a well-controlled biological system the main molecular and geochemical processes affected by small As(V) concentrations using state-of-the art analytical and molecular techniques. This study will simultaneously provide new information on Shewanella and a model for what may occur in natural environments. This work will also provide novel information on the genes and gene products affected by the addition of low concentrations of As(V) in iron-reducing bacteria. While the influence of mineral oxides on trace metal speciation in aquatic systems is well known, the effect of trace metal concentrations on the transformation of mineral oxides is not well recognized. This work will provide the first evidence that Fe respiration is enhanced by a toxic compound and that the structure and reactivity of Fe oxides is affected by these processes. As Fe oxides play a fundamental role as scavengers of contaminants, this work will have ramifications on the fate of other contaminants in aquaticsystems. Metalloids are among the most toxic inorganic pollutants in aquatic systems but, surprisingly, their presence in water reservoirs receives little attention as their concentration is generally low. This study will demonstrate that even low concentrations of a toxic metal affect these ecosystems by altering biological and geochemical processes.

在自然环境中，亚砷酸盐（As（III））不仅比砷酸盐（As（V））或有机砷化合物更具有移动的，而且毒性更大。尽管在实验室或水生系统中获得了丰富的知识，显示出显着的高浓度的砷，很少有研究已经进行了低砷输入到自然水生系统的影响。孵化与沉积物从格鲁吉亚河显示，低（10 μ M），但不断增加的As（V）浓度刺激增加微生物铁还原率伴随着二次重结晶的铁氧化物。本研究将探讨低浓度砷对铁还原菌对铁氧化物的厌氧呼吸作用的影响机制。据推测，砷（V）刺激铁还原菌的能量产生过程中的磷酸盐的磷酸化ADP的砷酸盐取代。这种效应被假定是由于在磷酸盐限制条件下铁还原细菌表达磷酸盐转运蛋白及其调节剂所致。最后，亚微摩尔As（V）浓度在自然环境中对微生物Fe还原的巨大影响被假设为来自催化循环，由此通过微生物解毒产生的As（III）通过Mn（IV）氧化物的化学氧化迅速再循环为As（V），该氧化物普遍存在于自然环境中。一系列的培养与纯培养的金属还原希瓦氏菌的目的是调查在一个良好控制的生物系统中的主要分子和地球化学过程的影响，小As（V）的浓度，使用国家的最先进的分析和分子技术。这项研究将同时提供关于希瓦氏菌的新信息，并为自然环境中可能发生的情况提供模型。这项工作也将提供新的信息，在铁还原细菌中加入低浓度的As（V）的基因和基因产物的影响。虽然矿物氧化物对水生系统中微量金属形态的影响是众所周知的，但微量金属浓度对矿物氧化物转化的影响还没有得到很好的认识。这项工作将提供的第一个证据表明，铁呼吸是由有毒化合物和铁氧化物的结构和反应性的影响，这些过程。由于铁氧化物作为污染物的清除剂发挥着重要作用，这项工作将对水生系统中其他污染物的命运产生影响。类金属是水生系统中毒性最大的无机污染物之一，但令人惊讶的是，它们在水库中的存在很少受到关注，因为它们的浓度通常很低。这项研究将表明，即使是低浓度的有毒金属也会通过改变生物和地球化学过程来影响这些生态系统。