Engineered plant–microbe symbiosis enables aerobic upcycling of wastewater heavy metal into photosynthetic semiconductor biohybrids

Refined Abstract Plants naturally extract heavy metals from polluted water, but they merely accumulate these toxins in their tissues, leaving behind hazardous biomass. Alternatively, microbial biomineralization can precipitate dissolved metals into valuable semiconductor nanomaterials, but this process relies on sulfate-reducing bacteria, strict anaerobes that cannot survive the oxygen-rich environment of plant roots. Here we overcome this oxygen limitation by engineering the aerobic bacterium Vibrio natriegens to colonize water lettuce ( Pistia stratiotes ) roots and assemble metal sulfides directly in the rhizosphere. Sustained entirely by root exudates, the bacteria perform aerobic sulfate reduction to generate hydrogen sulfide, precipitating aqueous cadmium and lead into cell-surface-anchored CdS and PbS semiconductor nanoparticles (4.94–11.00 nm). The resulting semiconductor-cell biohybrids exhibit photoelectric properties, making them valuable for post-harvest applications such as solar-driven biosynthesis. Concurrently, bacterial auxin secretion buffers the host plant against metal toxicity, recovering root biomass by over 10%. Over consecutive treatment cycles, this system removed 30% of cadmium and 63% of lead from the aqueous phase, far exceeding the capacity of single-host controls. By decoupling sulfide biomineralization from anaerobic constraints, this rhizospheric strategy upgrades wastewater treatment from metal sequestration to optoelectronic material recovery.