Biomineralization Influences the Transport of Bacteria and Cell-Associated Nanoparticles in Saturated Porous Media

Understanding bacterial transport and fate in porous media is critical for effective bioremediation and water quality management. Although bacteria mediate (trans)formation of diverse nanoparticles, how biomineralization affects cell mobility remains unclear. Here, association with different biogenic nanoparticles was found to enhance the transport of mineralized Shewanella oneidensis MR-1 cells in quartz sand columns by altering bacterial viability, surface potential or hydrophobicity. Moreover, silver nanoparticle (AgNPs) biomineralization augmented extracellular electron transfer, energy taxis and redox responsiveness of resultant AgNPs-mineralized cells but impeded their mobility in ferrihydrite- and birnessite-coated columns. While quinone electron shuttles increased cell deposition in mineral-coated columns by stimulating energy taxis, natural humic acids promoted cell breakthrough through electrosteric repulsion. Negative tactic response toward abiogenic AgNPs induced enhanced breakthrough and pronounced blocking effects in bare sand column. Concurrence of negative chemotaxis toward abiogenic AgNPs and positive energy taxis toward ferrihydrite facilitated the transport of pristine MR-1, but restrained that of AgNPs-mineralized cells. Enhanced AgNPs-mineralized cells retention in ferrihydrite-coated columns further enabled AgNPs immobilization via microbial transformation of ferrihydrite to magnetite. In contrast, cell-associated AgNPs retained in birnessite-coated columns could be remobilized as nanoparticles via bioreductive birnessite dissolution or as Ag+ via birnessite oxidation, increasing the risk of silver dissemination.