Aix Marseille University, CEA, CNRS, BIAM, UMR 7265, Saint Paul-Lez-Durance France.
Aix Marseille University, CEA, CNRS, BIAM, UMR 7265, Saint Paul-Lez-Durance France
Appl Environ Microbiol. 2020 Jul 2;86(14). doi: 10.1128/AEM.00803-20.
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 within the genomes of two magnetotactic bacteria strains, AMB-1 and 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 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. Whole-cell biosensors based on reporter genes can be designed for heavy metal detection but often require the optimization of their sensitivity and specific adaptations for practical use in the field. Magnetotactic bacteria as cellular hosts for biosensors are interesting models, as their intrinsic magnetism permits them to be easily concentrated and entrapped to increase the arsenic-response signal. This paves the way for the development of sensitive and immobilized whole-cell biosensors tailored for use in the field.
根据世界卫生组织的数据，砷是影响全球人口最多的水污染物质。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，这种传感器已经被广泛研究，可以满足所有这些标准，尽管它们通常缺乏灵敏度。在这里，我们研究了利用磁细菌作为细胞底盘来设计和构建灵敏的磁性细菌生物传感器的好处。首先在两种磁细菌菌株 AMB-1 和 MSR-1 的基因组中鉴定出潜在可被砷诱导的启动子。通过反转录-PCR 实验证实了 ArsR 依赖性调控。通过将砷诱导启动子与细菌荧光素操纵子进行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，亚砷酸盐检测限为 0.5 μM。经过磁浓缩后，我们通过将生物传感器的灵敏度提高了 50 倍，达到了 10 nM，比饮用水中砷的推荐标准（0.13 μM）低了 1 个数量级。最后，我们通过冷冻干燥成功地保存了磁性细菌生物传感器。基于报告基因的全细胞生物传感器可用于重金属检测，但通常需要优化其灵敏度和特定的适应性，以在现场实际使用。作为生物传感器的细胞宿主，磁细菌是一种很有趣的模型，因为它们的固有磁性允许它们被轻松浓缩和捕获，以增加砷响应信号。这为开发用于现场的灵敏和固定化全细胞生物传感器铺平了道路。
