Conventional physical and chemical treatments can remove over 90% of heavy metals, but they often require energy-intensive steps and can generate secondary pollution. Phytoremediation is greener, yet plants mainly store metals in biomass, creating hazardous waste rather than recoverable products. Microbial biomineralization can make valuable metal sulfide nanomaterials, but many high-performing sulfide-producing microbes are sulfate-reducing bacteria that grow slowly and are inhibited by oxygen, including oxygen released from plant roots. Common rhizobacteria can alleviate metal stress, but they usually need external cysteine or other sulfur supplements to form metal sulfides. Given these challenges, in-depth research is needed on oxygen-tolerant, root-colonizing microbial systems that can couple wastewater treatment with heavy-metal upcycling.
Researchers from Harbin Institute of Technology (Shenzhen), Shenzhen Polytechnic University, Zhejiang Shuren University and the Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, report (DOI: 10.1016/j.ese.2026.100780). the system in Environmental Science and Ecotechnology. The article was accepted on 21 October 2026 and is available as a Journal Pre-proof (final Version of Record not yet assigned). The team engineered Vibrio natriegens to colonize water lettuce (Pistia stratiotes) roots and assemble cadmium sulfide (CdS) and lead sulfide (PbS) nanoparticles in the rhizosphere under aerobic conditions, then characterized metal removal, plant physiology and biohybrid photoelectric properties.
The engineered strain, XG203, carries cdsH, which encodes cysteine desulfhydrase, and a mutant cysE, which encodes serine acetyltransferase. It uses root exudates—mainly fatty acids, phosphates, alcohols, carbohydrates, amines and organic acids—to support growth. After inoculation, the bacteria colonized root crowns and root hairs within 24 hours. In aerobic culture, the strain reduced sulfate and generated hydrogen sulfide (H₂S), precipitating Cd²⁺ and Pb²⁺ as cell-surface-anchored CdS and PbS nanoparticles. Isolated CdS particles averaged about 4.94 nanometers (nm), showed cubic crystallinity, a direct bandgap of about 2.44 electron volts (eV) and photocurrent response. Over two treatment cycles, the plant–bacteria system maintained average per-cycle removal efficiencies of 30.12% for Cd and 63.50% for Pb from the aqueous phase, outperforming plants alone; free-living bacteria removed less than 3.03%. The bacteria also secreted indole-3-acetic acid (IAA), increasing root dry weight by 11.50% under Cd stress and 10.04% under Pb stress relative to uninoculated stressed plants. Photosystem I (PSI) metrics improved with inoculation, indicating reduced metal-induced photosynthetic impairment. The authors estimate that about 9.89% of Cd and 8.93% of Pb were associated with bacterial biohybrids, with the rest distributed among plant tissues and matrix-associated fractions.
The authors said the advance lies in moving sulfide biomineralization from oxygen-sensitive anaerobic niches into the oxygen-rich rhizosphere. They said the engineered bacterium uses root exudates to support growth without an external carbon source in the plant–bacteria system, couples aerobic sulfate reduction to metal capture, and turns a treatment liability into a photoelectrically active material. They said the system also supports the host plant by supplying IAA, helping roots recover biomass under metal stress. They said the next step is to test stability, microbial competition and biocontainment under field-relevant conditions.
The approach points to decentralized wastewater treatment and resource recovery, especially in constructed wetlands, agricultural runoff systems and other sites where long-term environmental compatibility matters. Recovered semiconductor–cell biohybrids could be used for solar-driven biosynthesis, photocatalysis or photoelectrochemical sensing, although they are recovered as root-associated materials rather than purified nanoparticles. Because metal sulfides have lower leaching potential than conventional hydroxide precipitates, the strategy may suit long-term restoration. The authors caution that performance will depend on sunlight, hydraulic residence time, ion interference and microbial competition. Field trials, long-term stability tests, biocontainment strategies and regulatory assessment are needed before responsible scale-up in real wastewater systems.
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References
DOI
10.1016/j.ese.2026.100780
Original Source URL
https://doi.org/10.1016/j.ese.2026.100780
Funding information
This work was financially supported by the National Key Research and Development Program of China (2023YFD1701402), National Natural Science Foundation of China(52470071 and 52321005), State Key Laboratory of Urban-rural Water Resources and Environment (Harbin Institute of Technology) (No. 2025TS40), Shenzhen Science and Technology Program (JCYJ20240813092008011), and Natural Science Foundation of Guangdong Province (2023A1515012063), Project of Shenzhen Polytechnic University(6024310035K).
About Environmental Science and Ecotechnology
Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. The latest impact factor of ESE is 14.3, according to the Journal Citation ReportsTM 2024.