Abstract Cadmium pollution has become a serious environmental issue due to its toxicity and frequent entrance into environment components such as soil, water, and air via many anthropogenic sources. Over the last two decades, whole-cell bacterial bioreporters have been acknowledged as bio-sentinels for the determination of toxic heavy metals. Herein a sensitive and quite specific bacterial bioreporter was developed to cope with the need for the rapid and simple determination of cadmium. The construction and characterization of a fluorescence-based whole-cell cadmium bioreporter strain, Escherichia coli MG1655 (pBR-PzntA), was described which is based on the expression of green fluorescent protein under the control of the zntA gene promoter of heavy metal resistance determinant. The developed bioreporter was able determine cadmium at 5 µg/L after 3.5 hours of induction in a defined medium while the cadmium detection limit was improved to 2 µg/L after 1.5 hours by the use of an inorganic phosphate-limiting defined medium. Drastic changes in cadmium sensitivity were obtained between bioreporter cells induced at different growth phases. The maximum fluorescence performance was obtained for early exponential growth phase cells. This cadmium bioreporter was found to be more sensitive and specific to cadmium ions than to a wide range of heavy metals and was sensitive to only cadmium at drinking water quality standard concentrations. These findings will lead to future studies including integration of the bioreporter cells into a portable device to assess bioavailable cadmium levels in environmental samples which will provide a rapid and practical field detection technique.

中文翻译：

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使用荧光全细胞细菌生物报告剂进行无机镉检测

摘要 镉污染由于其毒性和通过多种人为来源频繁进入土壤、水和空气等环境成分，已成为一个严重的环境问题。在过去的二十年中，全细胞细菌生物报告基因已被公认为测定有毒重金属的生物哨兵。在此开发了一种灵敏且非常特异的细菌生物报告基因，以应对快速简单测定镉的需要。描述了基于荧光的全细胞镉生物报告菌株大肠杆菌 MG1655 (pBR-PzntA) 的构建和表征，该菌株基于在重金属抗性决定簇 zntA 基因启动子控制下的绿色荧光蛋白的表达. 开发的生物报告器能够在 3 后测定 5 µg/L 的镉。在限定培养基中诱导 5 小时，而通过使用无机磷酸盐限定限定培养基，1.5 小时后镉检测限提高到 2 µg/L。在不同生长阶段诱导的生物报告细胞之间获得了镉敏感性的急剧变化。对于早期指数生长期细胞，获得了最大的荧光性能。发现这种镉生物报告基因对镉离子的敏感性和特异性高于对多种重金属的敏感性，并且仅对饮用水质量标准浓度的镉敏感。这些发现将导致未来的研究，包括将生物报告细胞整合到便携式设备中，以评估环境样品中的生物可利用镉水平，这将提供一种快速实用的现场检测技术。