Insights into the enhanced transport across membranes in self-regenerable biohybrid with ferrous sulfide for photo-assisted uranium reduction fixation.

Bioreduction is considered to be one of the most effective methods for the bioremediation of uranium-contaminated soil or water, in which the low extracellular electron transfer (EET) rate of microorganisms seriously affects the reduction and fixation of uranium through microorganisms. Here, we develop an in-situ self-regenerable Shewanella putrefaciens (S. putrefaciens)-FeS biohybrid system to enhance the efficiency of uranium reduction. The dense layer of bio-FeS on the cell surface of S. putrefaciens provides excellent uranium tolerance and activity for bio-FeS-mediated uranium reduction. Bio-FeS constructs an artificial transmembrane electron channel that facilitates extracellular electron transfer, enabling efficient regeneration of extracellular bio-FeS for continuous uranium reduction. Notably, the S. putrefaciens-FeS biohybrid system exhibits excellent uranium removal ability with a removal capacity of up to 94% in real uranium mine wastewater compared with pristine S. putrefaciens (48%). In addition, by virtue of various spectroscopic and multi-omics techniques, we confirm that the presence of bio-FeS promotes the secretion of more extracellular polymeric substances (EPS) and riboflavin, significantly improving the intracellular metabolism and EET efficiency of bacteria for uranium reduction. Relying on X-ray absorption fine spectroscopy (XAFS) and density functional theory (DFT) calculations, we have confirmed that the oxygen-containing functional groups of phosphatidic acid and amino acid on the surface of biohybrid membranes achieve uranyl selective coordination via interlocking structures. This work deepens understanding of the electron transport mechanisms involved in mineral and microorganism systems, and also provides theoretical references for the in-situ biological purification of uranium-contaminated soil or water.