Time-Dependent Biosensor Fluorescence as a Measure of Bacterial Arsenic Uptake Kinetics and Its Inhibition by Dissolved Organic Matter
Time-Dependent Biosensor Fluorescence as a Measure of Bacterial Arsenic Uptake Kinetics and Its Inhibition by Dissolved Organic Matter
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DOI：
10.1128/aem.00891-22
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发表时间：
2022-08-01
影响因子：
4.4
通讯作者：
Reid，Matthew C.
中科院分区：
文献类型：
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作者：
Yoon，Hyun;Giometto，Andrea;Reid，Matthew C.
微生物介导的砷（As）转化通常需要在酶促反应之前将砷吸收到细胞中。尽管这些微生物反应对砷的形成和毒性具有重要意义，但对细胞外水化学（特别是溶解有机物（DOM））如何调节砷的生物利用度和吸收的理解仍然有限。利用荧光蛋白的全细胞生物传感器越来越多地用于高通量定量水中砷的生物可利用部分。在这里，我们提出了一个数学框架来解释生物传感器荧光的时间序列作为砷摄取动力学的测量，我们用它来评估不同形式的DOM对三价亚砷酸盐摄取的影响。我们发现含硫醇的有机化合物显著抑制亚砷酸盐进入细胞，可能是通过在亚砷酸盐和硫醇配体之间形成水络合物。虽然没有证据表明亚砷酸盐和低分子量中性分子（尿素、甘氨酸和甘油醛）通过水甘油孔蛋白通道GlpF（介导亚砷酸盐跨细胞膜运输）摄取时存在竞争性相互作用，但有证据表明，不稳定的DOM组分可能通过分解代谢物抑制样机制抑制亚砷酸盐的摄取。观察到湿地孔隙水中常见的DOM/As对亚砷酸盐吸收的显著抑制，表明DOM可能是环境中微生物对亚砷酸盐吸收的重要控制因素，DOM质量方面在抑制程度上起着重要作用。重要性砷在稻田土壤和地下水含水层等环境中的形态和毒性受微生物介导的反应控制。这些反应通常需要在酶促反应之前将砷吸收到细胞中，但是对水化学变化如何影响微生物对砷的吸收的了解有限。在这项研究中，我们探讨了溶解有机物（DOM）的数量和质量对微生物砷吸收的影响，重点研究了硫醇官能团的作用，硫醇官能团是众所周知的与砷形成水络合物的物质。我们开发了一个定量框架，用于解释全细胞生物传感器的荧光时间序列，并使用该技术评估DOM对微生物砷吸收速率的影响。我们发现，在环境相关的DOM/As比率下，含硫醇的化合物显著降低了微生物细胞对砷的吸收速率，揭示了DOM质量在调节砷在环境中的吸收和随后的生物转化中的重要性。
Microbe-mediated transformations of arsenic (As) often require As to be taken up into cells prior to enzymatic reaction. Despite the importance of these microbial reactions for As speciation and toxicity, understanding of how As bioavailability and uptake are regulated by aspects of extracellular water chemistry, notably dissolved organic matter (DOM), remains limited. Whole-cell biosensors utilizing fluorescent proteins are increasingly used for high-throughput quantification of the bioavailable fraction of As in water. Here, we present a mathematical framework for interpreting the time series of biosensor fluorescence as a measure of As uptake kinetics, which we used to evaluate the effects of different forms of DOM on uptake of trivalent arsenite. We found that thiol-containing organic compounds significantly inhibited uptake of arsenite into cells, possibly through the formation of aqueous complexes between arsenite and thiol ligands. While there was no evidence for competitive interactions between arsenite and low-molecular-weight neutral molecules (urea, glycine, and glyceraldehyde) for uptake through the aquaglyceroporin channel GlpF, which mediates transport of arsenite across cell membranes, there was evidence that labile DOM fractions may inhibit arsenite uptake through a catabolite repression-like mechanism. The observation of significant inhibition of arsenite uptake at DOM/As ratios commonly encountered in wetland pore waters suggests that DOM may be an important control on the microbial uptake of arsenite in the environment, with aspects of DOM quality playing an important role in the extent of inhibition.IMPORTANCEThe speciation and toxicity of arsenic in environments like rice paddy soils and groundwater aquifers are controlled by microbe-mediated reactions. These reactions often require As to be taken up into cells prior to enzymatic reaction, but there is limited understanding of how microbial arsenic uptake is affected by variations in water chemistry. In this study, we explored the effect of dissolved organic matter (DOM) quantity and quality on microbial As uptake, with a focus on the role of thiol functional groups that are well known to form aqueous complexes with arsenic. We developed a quantitative framework for interpreting fluorescence time series from whole-cell biosensors and used this technique to evaluate effects of DOM on the rates of microbial arsenic uptake. We show that thiol-containing compounds significantly decrease rates of As uptake into microbial cells at environmentally relevant DOM/As ratios, revealing the importance of DOM quality in regulating arsenic uptake, and subsequent biotransformation, in the environment.