Pothier Martin P, Hinz Aaron J, Poulain Alexandre J
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Front Microbiol. 2018 Oct 2;9:2310. doi: 10.3389/fmicb.2018.02310. eCollection 2018.
Despite its high toxicity and widespread occurrence in many parts of the world, arsenic (As) concentrations in decentralized water supplies such as domestic wells remain often unquantified. One limitation to effective monitoring is the high cost and lack of portability of current arsenic speciation techniques. Here, we present an arsenic biosensor assay capable of quantifying and determining the bioavailable fraction of arsenic species at environmentally relevant concentrations. First, we found that inorganic phosphate, a buffering agent and nutrient commonly found in most bioassay exposure media, was in fact limiting As(V) uptake, possibly explaining the variability in As(V) detection reported so far. Second, we show that the nature of the carbon source used in the bioassay differentially affects the response of the biosensor to As(III). Finally, our data support the existence of non-specific reduction pathways (non- encoded) that are responsible for the reduction of As(V) to As(III), allowing its detection by the biosensor. To validate our laboratory approach using field samples, we performed As(III) and As(V) standard additions on natural water samples collected from 17 lakes surrounding Giant Mine in Yellowknife (NWT), Canada. We found that legacy arsenic contamination in these lake water samples was accurately quantified by the biosensor. Interestingly, bioavailability of freshly added standards showed signs of matrix interference, indicative of dynamic interactions between As(III), As(V) and environmental constituents that have yet to be identified. Our results point toward dissolved organic carbon as possibly controlling these interactions, thus altering As bioavailability.
尽管砷（As）具有高毒性且在世界许多地区广泛存在，但分散式供水（如家庭水井）中的砷浓度往往仍未得到量化。有效监测的一个限制因素是当前砷形态分析技术成本高昂且缺乏便携性。在此，我们展示了一种砷生物传感器检测方法，它能够在与环境相关的浓度下对砷物种的生物可利用部分进行定量和测定。首先，我们发现无机磷酸盐作为大多数生物检测暴露介质中常见的缓冲剂和营养物质，实际上限制了五价砷（As(V)）的吸收，这可能解释了迄今为止报道的五价砷检测结果的变异性。其次，我们表明生物检测中使用的碳源性质对生物传感器对三价砷（As(III)）的响应有不同影响。最后，我们的数据支持存在非特异性还原途径（非编码），这些途径负责将五价砷还原为三价砷，从而使其能够被生物传感器检测到。为了使用现场样本验证我们的实验室方法，我们对从加拿大西北地区耶洛奈夫巨人矿周围17个湖泊采集的天然水样进行了三价砷和五价砷标准添加实验。我们发现这些湖水样本中的遗留砷污染通过生物传感器得到了准确量化。有趣的是，新添加标准物的生物可利用性显示出基质干扰的迹象，这表明三价砷、五价砷与尚未确定的环境成分之间存在动态相互作用。我们的结果表明溶解有机碳可能控制着这些相互作用，从而改变了砷的生物可利用性。
