According to the World Health Organization, arsenic is the water contaminant that affects the largest number of people worldwide. To limit its impact on the population, inexpensive, quick, and easy-to-use systems of detection are required. One promising solution could be the use of whole-cell biosensors, which have been extensively studied and could meet all these criteria even though they often lack sensitivity. Here, we investigated the benefit of using magnetotactic bacteria as cellular chassis to design and build sensitive magnetic bacterial biosensors. Promoters potentially inducible by arsenic were first identified in silico within the genomes of two magnetotactic bacteria strains, Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1. The ArsR-dependent regulation was confirmed by reverse transcription-PCR experiments. Biosensors built by transcriptional fusion between the arsenic-inducible promoters and the bacterial luciferase luxCDABE operon gave an element-specific response in 30 min with an arsenite detection limit of 0.5 μM. After magnetic concentration, we improved the sensitivity of the biosensor by a factor of 50 to reach 10 nM, more than 1 order of magnitude below the recommended guidelines for arsenic in drinking water (0.13 μM). Finally, we demonstrated the successful preservation of the magnetic bacterium biosensors by freeze-drying.

中文翻译：

---

趋磁细菌中托管的一种特定于砷的敏感磁性生物传感器。

根据世界卫生组织的说法，砷是影响全球最大数量人口的水污染物。为了限制其对人群的影响，需要廉价，快速且易于使用的检测系统。一种有前途的解决方案可能是使用全细胞生物传感器，该传感器已被广泛研究，即使它们通常缺乏敏感性，也可以满足所有这些标准。在这里，我们研究了使用趋磁细菌作为细胞底盘来设计和构建敏感的磁性细菌生物传感器的好处。首先在两个趋磁细菌菌株Magnetospirillum magneticum AMB-1和Magnetospirillum gryphiswaldense的基因组中通过计算机模拟鉴定了可能被砷诱导的启动子。MSR-1。通过逆转录PCR实验证实了ArsR依赖性调节。通过砷诱导型启动子和细菌荧光素酶luxCDABE操纵子之间的转录融合构建的生物传感器在30分钟内给出了元素特异性响应，砷的检出限为0.5μM。磁浓缩后，我们将生物传感器的灵敏度提高了50倍，达到10 nM，比饮用水中砷的推荐指南（0.13μM）低了一个数量级。最后，我们证明了通过冷冻干燥成功保存了磁性细菌生物传感器。