Rational design of a dual-bacterial system for synchronous removal of antibiotics and Pb(Ⅱ)/Cd(Ⅱ) from water

Facing the combined pollution of antibiotics and heavy metals caused by livestock excrement and industrial effluents, how to use microbial technology to remove these pollutants simultaneously is an important research topic in environmental remediation. In addition, quick separation of the bacteria-water after remediation is also an urgent problem. In this study, we gradually developed a dual-bacteria microbial treatment technology capable of removing Pb(Ⅱ), Cd(Ⅱ) and common antibiotics, as well as self-settling after treatment. The key technology in this study mainly includes modifying the bacterial membrane proteins using Pb-binding protein PbrR, Cd-binding protein CadR and bacterial laccase CotA via surface-display technology to maximize the removal of Pb(Ⅱ), Cd(Ⅱ) and antibiotics, separately. Besides, the introduction of nanobody-antigen adhesion facilitated the self-settling in dual-bacterial system. Then, we studied its effectiveness in removing single pollutants, analyzed the influence of different heavy metal ions, and conducted detailed studies on the kinetics. Further characterization of heavy metal biosorption behavior was conducted using SEM, SEM-EDS, FTIR, and XPS techniques. Via protein fusion and dual vector expression, we constructed a dual-bacteria treatment system that could achieve rapid, selective removal of combined pollutants at a wide pH range temperature range, ultimately precipitating at bottom. Finally, molecular dynamics simulation was employed to elucidate the molecular mechanism underlying the selective biosorption by metal-binding proteins. The findings in this study hold significant implications for achieving selective pollutant removal using engineering bacteria in complex water environments.