Altering the Biotransformation Fate of Mercury by Coordinating Respiratory, Electron Flow, and Trapping Module

Dissimilatory metal-reducing bacteria (DMRB) have the talent to convert mercury ions (Hg²⁺) into elemental mercury (Hg⁰). Here, we shed light on the directed biomineralization of Hg²⁺ into mercury selenide (HgSe), which is a promising environmental sink for Hg with minimal ecological risk. This process displays a controlled subcellular localization, improved efficiency, and redistribution of Hg species through the coordination of three modules, including reinforced respiratory, reconfigured electron flow, and anchored trap in Shewanella oneidensis MR-1, a model DMRB. By supplementing redox substance, we first construct a golden Hg²⁺ capture system, that is S. oneidensis-Se⁰ hybrid. Redox substance triggers a transition from intracellular selenite reduction to extracellular biosynthesis of Se⁰ nanoparticles (NPs), resulting in a notably increased yield of Se⁰ NPs. Importantly, this hybrid alters the biotransformation fate of Hg²⁺, enabling the efficient formation of less toxic HgSe nanoparticles and decreasing the percentage of volatile Hg⁰. Such a biological decontamination process relies on sufficient bioelectron donation, unimpeded electron channels, and highly effective Hg²⁺ traps, all of which can be initiated, directed, and coordinated by the redox-active compound. The resulting S. oneidensis-Se⁰ hybrid is feasible to scale up for the depuration of Hg²⁺ in artificial wastewater by using a membrane bioreactor (MBR). Our work provides an integrated strategy for designing biological capture to immobilize Hg²⁺, offering fundamental guidance to improve biotechnologies in environmental remediation and resource recovery.