Department of Plant and Microbial Biology, University of California Berkeley, Koshland Hall, Berkeley, CA, 94720, USA.
QB3, University of California Berkeley, Stanley Hall, Berkeley, CA, 94720, USA.
Sci Rep. 2020 Sep 15;10(1):15091. doi: 10.1038/s41598-020-72138-9.
Engineering bacteria to clean-up oil spills is rapidly advancing but faces regulatory hurdles and environmental concerns. Here, we develop a new technology to harness indigenous soil microbial communities for bioremediation by flooding local populations with catabolic genes for petroleum hydrocarbon degradation. Overexpressing three enzymes (almA, xylE, p450cam) in Escherichia coli led to degradation of 60-99% of target hydrocarbon substrates. Mating experiments, fluorescence microscopy and TEM revealed indigenous bacteria could obtain these vectors from E. coli through several mechanisms of horizontal gene transfer (HGT), including conjugation and cytoplasmic exchange through nanotubes. Inoculating petroleum-polluted sediments with E. coli carrying the vector pSF-OXB15-p450camfusion showed that the E. coli cells died after five days but a variety of bacteria received and carried the vector for over 60 days after inoculation. Within 60 days, the total petroleum hydrocarbon content of the polluted soil was reduced by 46%. Pilot experiments show that vectors only persist in indigenous populations when under selection pressure, disappearing when this carbon source is removed. This approach to remediation could prime indigenous bacteria for degrading pollutants while providing minimal ecosystem disturbance.
利用工程菌清除溢油污染技术发展迅速，但面临监管障碍和环境问题。在这里，我们开发了一种新技术，通过向当地土著土壤微生物群落中大量导入石油烃降解的代谢基因来进行生物修复。在大肠杆菌中过表达三种酶（almA、xylE、p450cam），可导致 60-99%的目标烃类底物降解。接合实验、荧光显微镜和 TEM 显示，土著细菌可以通过多种水平基因转移（HGT）机制从大肠杆菌中获得这些载体，包括通过纳米管进行接合和细胞质交换。将携带载体 pSF-OXB15-p450camfusion 的大肠杆菌接种到石油污染的沉积物中，结果表明大肠杆菌细胞在五天后死亡，但在接种后 60 多天内，多种细菌接收并携带了该载体。在 60 天内，污染土壤中的总石油烃含量减少了 46%。初步实验表明，只有在选择压力下，载体才能在土著种群中存在，当去除这种碳源时，载体就会消失。这种修复方法可以使土著细菌优先降解污染物，同时最小化对生态系统的干扰。
