Production of copper nanoparticles by Morganella psychrotolerans
There is growing interest in copper nanoparticles for their potential role in industrial catalysis and as antimicrobial agents. However, their chemical synthesis requires strong reducing agents and high temperatures. Using living cells to synthesise copper nanoparticles can overcome these requirements, but the mechanism of this biological synthesis is not well understood. Better understanding and control of the synthesis mechanism will allow the scale up of biological production methods, and presents opportunities in the remediation of copper ions from industrial waste streams, such as those produced by the distillery industry. Morganella psychrotolerans has previously been shown to convert copper (II) ions to stable copper (0) nanoparticles at room temperature. It can tolerate high concentrations of copper and grow in whisky co-products. The aim of this study was to better understand the mechanism of copper nanoparticle formation in Morganella psychrotolerans through the investigation of the proteins involved. For the first time, proteomic analysis of the cell’s response to copper exposure was carried out using mass spectrometry. The cellular proteins stabilising the copper nanoparticles were also identified and described. Selected proteins from these analyses were constitutively overexpressed to quantify their effect on nanoparticle production and their effect on the reductive capacity of the cell milieu. In order to develop genetic tools to modify these proteins, both homologous recombination and CRISPR-Cas9 were trialled in Morganella psychrotolerans.