The molecular ecology of arsenic; probing the biogeochemical basis of a humanitarian disaster

砷的分子生态学；

• 批准号: NE/D014069/1
• 负责人: Jonathan Lloyd
• 金额: $ 4.44万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD014069%2F1
• 关键词: molecular; ecology; arsenic; probing; biogeochemical

The use of groundwaters containing high concentrations of arsenic for drinking and irrigation is poisoning millions worldwide. For example, in West Bengal and Bangladesh arsenic levels can reach mg quantities of arsenic per litre of water, and this has led to what has been described as 'the worst mass poisoning in human history'. Despite the urgent need for fundamental information in the mechanism of arsenic release from sediments into water, the causes of this humanitarian disaster remain controversial. Several possible mechanisms may release arsenic sorbed to minerals in the sediments, and all have been debated vigorously. These include changes in the sediment minerals from the oxidation of arsenic-rich pyrite in the upper regions of the aquifers or the breakdown of arsenic-rich Fe(III) oxyhydroxides under reducing conditions deeper in the sediments, while other ions in the water could also mobilise sorbed arsenic e.g. phosphate or carbonate. Although these changes are chemical, there is a growing consensus that microorganisms in the sediments may well drive these reactions. Indeed, recent results from our laboratory have shown that specialist subsurface microorganisms mobilise the toxic arsenic sorbed to minerals in the sediments. Growing in the absence of oxygen, these 'metal-reducing bacteria' gain energy from the reduction of sorbed As(V) coupled to the oxidation of organic matter. With growing support from studies in other laboratories, there is now a consensus that this form of microbial metabolism plays a critical role in controlling arsenic concentrations in aquifer sediments worldwide. There is, however, little information on the identity of the bacteria responsible, and no model organisms on which to base 'geomicrobiological' studies on the mechanism of arsenic reduction and mobilisation in aquifers in the Ganges delta. This information is needed urgently to underpin remediation efforts or help develop safer practices for water use, as it is clearly very difficult to solve an environmental problem without a detailed understanding of the cause. The aim of this work is to address our limitations of the understanding of the mechanism of As mobilisation in aquifers by conducting a detailed and long overdue study of the microbiology of such an aquifer in W. Bengal, alongside the application of state of the art molecular biology techniques to identify the genes and proteins involved in arsenic release from the sediments. By feeding microbial communities with isotopically labeled organic matter (acetate and lactate as proxies for new organic matter drawn into the aquifers by water abstraction and petroleum which is an electron donor in deeper sediments), we will isolate the labeled nucleic acids synthesized from bacteria that are active in the sediments when arsenic is mobilised, and use genetic fingerprinting techniques to identify these 'active' bacteria, and the corresponding arsenic reducing/mobilising genes that they contain. As many of the arsenic genes will be novel, we will look for them in 'metagenomic libraries' which will contain large fragments of DNA from the sediments that encode both the As(V) reductase genes and other highly conserved marker genes that we can use to identify the bacteria accurately. This will be the first time that metagenomic library construction and screening has been used in this field to identify potentially novel As(V)-respiring bacteria without the need to culture them. Finally, so that we can gain a better picture of the role of these biological transformations in the arsenic cycle, we will also study the mineral phases and groundwater composition using state of the art mineralogical and geochemical techniques, while we are monitoring changes in the microbial communities and the genes that they are expressing. This will allow us to develop a detailed molecular-scale picture of the impact of microbial metabolism on the aqueous and mineral-bound forms of arsenic.

使用含有高浓度砷的地下水作为饮用水和灌溉用水正在使全世界数百万人中毒。例如，在西孟加拉和孟加拉国，砷含量可达到每升水含砷毫克，这导致了被称为“人类历史上最严重的大规模中毒”。尽管迫切需要关于沉积物中砷释放到水中的机制的基本信息，但这场人道主义灾难的原因仍然存在争议。几种可能的机制可能会释放砷吸附到沉积物中的矿物质，所有这些都受到了激烈的争论。这些变化包括富砷黄铁矿的氧化在上层地区的含水层或分解的富砷铁（三）羟基氧化物在还原条件下更深的沉积物中的沉积物矿物，而水中的其他离子也可以动员吸附砷，如磷酸盐或碳酸盐。虽然这些变化是化学变化，但越来越多的人认为沉积物中的微生物可能很好地驱动了这些反应。事实上，我们实验室最近的研究结果表明，专业的地下微生物可以调动沉积物中吸附到矿物质上的有毒砷。这些“金属还原菌”在缺氧条件下生长，从吸附的As（V）的还原和有机物的氧化中获得能量。随着其他实验室的研究越来越多的支持，现在有一个共识，即这种形式的微生物代谢在控制全球含水层沉积物中的砷浓度方面发挥着关键作用。然而，很少有信息的细菌负责的身份，并没有模式生物的基础上的“地质微生物学”的研究机制，砷的减少和动员在恒河三角洲的含水层。迫切需要这些信息来支持补救工作或帮助制定更安全的用水做法，因为如果不详细了解原因，显然很难解决环境问题。这项工作的目的是解决我们的理解的机制，作为动员在含水层中进行详细的和早该进行的研究，这样一个含水层的微生物学在W。孟加拉，以及最先进的分子生物学技术的应用，以确定基因和蛋白质参与砷释放的沉积物。通过用同位素标记的有机物喂养微生物群落（乙酸盐和乳酸盐作为通过取水和石油（石油是更深沉积物中的电子供体）吸入含水层的新有机物质的替代物），我们将分离由砷被动员时在沉积物中活跃的细菌合成的标记核酸，并使用遗传指纹技术来识别这些“活跃”细菌，以及它们所包含的相应的砷还原/动员基因。由于许多砷基因将是新的，我们将在“宏基因组文库”中寻找它们，这些文库将包含来自沉积物的大片段DNA，这些DNA编码As（V）还原酶基因和其他高度保守的标记基因，我们可以用它们来准确识别细菌。这将是宏基因组文库构建和筛选首次用于该领域，以鉴定潜在的新型As（V）呼吸细菌，而无需培养它们。最后，为了更好地了解这些生物转化在砷循环中的作用，我们还将使用最先进的矿物学和地球化学技术研究矿物相和地下水成分，同时监测微生物群落及其表达的基因的变化。这将使我们能够开发一个详细的分子尺度上的微生物代谢对水和矿物结合形式的砷的影响。

项目成果

The role of indigenous microorganisms in the biodegradation of naturally occurring petroleum, the reduction of iron, and the mobilization of arsenite from west bengal aquifer sediments.

• DOI: 10.2134/jeq2008.0223
• 发表时间: 2009-07
• 期刊: Journal of environmental quality
• 影响因子: 2.4
• 作者: H. Rowland;C. Boothman;R. Pancost;A. Gault;D. Polya;J. Lloyd