Fellow Co-investigators from work package 2 of Elemental Mission Hub, including Jonathan R Lloyd, Jennifer S Cavet, and Sarah J Haigh of University of Manchester and Thomas A Clarke of University of East Anglia, also contributed.
Summary:
In our latest study, we discovered how a common environmental bacterium, Shewanella oneidensis, can turn dissolved copper into useful nanoparticles. We found that a specific enzyme, known as HyaB (a [NiFe] hydrogenase), uses hydrogen to drive this transformation, helping the cells convert copper ions into stable copper nanoparticles. The process happens during anaerobic respiration, where the bacteria oxidise hydrogen via HyaB to release electrons, and those electrons are then used to reduce copper. By combining targeted gene knockouts, aqueous chemical analysis, and high-resolution electron microscopy, we linked HyaB activity directly to nanoparticle formation and visualised their production in the periplasm. Remarkably, the particles proved effective as catalysts in “click chemistry” reactions, showing how microbes could help us both clean up liquid wastes containing copper and create valuable new materials in a sustainable way. Looking ahead, this work can be used as a template for using engineering biology to enhance and fine-tune microbes for the tailored production of nanomaterials.
Abstract:
Shewanella oneidensis MR-1 can biosynthesize cell-supported Cu-nanoparticles (CuNPs), via the bioreduction of Cu(II)(aq), with excellent catalytic activity for click chemistry reactions. However, enzymatic mechanisms underpinning Cu(II) bioreduction were unclear. Here, the oxidation of hydrogen as electron donor was essential for Cu(II) bioreduction by S. oneidensis and hydrogenase deletion mutants were used to demonstrate the critical role of the periplasmic [NiFe] hydrogenase, HyaB. Wild type (WT) cultured cells coupled hydrogen oxidation to biosynthesis of Cu(0)/Cu(I)-NPs within the periplasm (identified using XRD and TEM with SAED, EDS, EELS); ΔhyaB mutants did not produce CuNPs. Biosynthesized CuNPs were catalytically active for the cycloaddition of methyl azidoacetate and 1-hexyne, confirming the potential for microbial revalorization of Cu(II)-containing wastewaters, by forming catalytically active nanomaterials. Identifying HyaB, as a key mediator for Cu(II) reduction in S. oneidensis is an important first step towards developing industrial bioprocesses for Cu(II) recovery and CuNP synthesis, offering a template for improvements using engineering biology. Interestingly, c-type cytochromes, critical for reduction of other metals, were unable to fully reduce Cu(II)(aq) in vivo despite being capable of Cu(II) reduction under in vitro conditions. In fact, Cu inhibited outer membrane cytochrome mediated reduction of Pd(II), and this may impact bioreduction of mixed metal solutions/effluents.
Byrd, N., Egan Morriss, C., Parker, J., Cai, R., Nunn, E. J., van Wonderen, J. H., Cavet, J. S., Parmeggiani, F., Kimber, R. L., Gralnick, J. A., Clarke, T. A., Haigh, S. J., & Lloyd, J. R. (2025). Hydrogenase Mediated Biosynthesis of Catalytically Active Cu Nanoparticles. Small, Article 2500210. Advance online publication. https://doi.org/10.1002/smll.202500210