Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.
J Appl Microbiol. 2019 Oct;127(4):1125-1134. doi: 10.1111/jam.14399. Epub 2019 Aug 9.
Escherichia coli is the conventional choice as the host strain for whole-cell bioreporter construction due to its well-understood genetics and well-established cloning protocols. However, for real-world environmental biosensing applications, it is often beneficial to use a bacterial strain derived directly from the environment under study to better ensure chemical target specificity and optimal response time. The aim of this study was to develop a whole-cell bioreporter for detection of bioavailable mercury by replacing E. coli with a wild-type bacterial host derived from a soil environment.
In this study, an Enterobacter cloacae strain isolated from soil derived from a municipal and electronic waste dumping site was engineered to serve as a bioluminescent bioreporter for mercury toxicity by linking its merR-like gene and promoter sequence to a reorganized luxABCDE gene cassette from Photorhabdus luminescens. This bioreporter, designated as E. cloacae DWH4 , detected mercury (HgCl ) at a minimum concentration of 0·2 µg l with a linear response profile being maintained between a range of 0·4-1600 µg l (R = 0·9604) with a peak bioluminescent response occurring within 1 h after exposure. No significant synergistic or antagonistic influences were observed on the bioluminescent response by other contaminating metal elements. Enterobacter cloacae DWH4 was also demonstrated to detect mercury effectively in artificially contaminated water sample with linear correlation (R = 0·9623).
The results indicated that E. cloacae DWH4 could detect mercury in quantities below the US Environmental Protection Agency's permitted limit values (2 µg l ). Hence, it is concluded that E. cloacae DWH4 has the potential to serve as an effective whole-cell bioreporter for the environmental monitoring of mercury contamination.
This study provides new insight into the recruitment of mercury-tolerant bacterial hosts derived from environmental samples over the conventional lab-based E. coli host for the construction of mercury bioreporters. With improved response time and selectivity, the environmentally sourced bacteria can serve as an alternative host choice to improve biosensing technology in the near future.
由于大肠杆菌的遗传学和克隆技术已经得到了很好的理解和建立，因此它通常被用作全细胞生物报告器构建的常规宿主菌株。然而，对于实际的环境生物传感应用，使用直接从研究环境中衍生的细菌菌株通常更有益，因为这样可以更好地确保化学靶标特异性和最佳响应时间。本研究的目的是通过用源自土壤环境的野生型细菌宿主替代大肠杆菌来开发一种用于检测生物可利用汞的全细胞生物报告器。
在本研究中，从一个城市和电子废物倾倒场的土壤中分离出一种阴沟肠杆菌菌株，通过将其 merR 样基因和启动子序列与 Photorhabdus luminescens 中重新组织的 luxABCDE 基因盒连接，将其工程化为用于汞毒性的生物发光生物报告器。这种生物报告器被命名为阴沟肠杆菌 DWH4，可检测低至 0.2μg/l 的汞（HgCl 2 ），在 0.4-1600μg/l 范围内保持线性响应曲线（R 2 = 0.9604），暴露后 1 小时内出现峰值生物发光响应。其他污染金属元素对生物发光响应没有明显的协同或拮抗影响。还证明阴沟肠杆菌 DWH4 可以有效地检测人工污染水样中的汞，线性相关性（R 2 = 0.9623）。
结果表明，阴沟肠杆菌 DWH4 可以检测到低于美国环境保护署允许限值（2μg/l）的汞量。因此，可以得出结论，阴沟肠杆菌 DWH4 有可能成为一种有效的用于监测汞污染的全细胞生物报告器。
本研究为从环境样本中招募耐汞细菌宿主替代传统实验室大肠杆菌宿主构建汞生物报告器提供了新的见解。通过提高响应时间和选择性，来源于环境的细菌可以作为替代宿主选择，以提高未来不久的生物传感技术。
