Nanoparticulate materials are used widely in society now and their toxicity in the environment is studied in the group. Aside from the physical chemistry measurements of nanoparticle fate, we are also looking at an organism-level response to bacteria with the model bacterium, Escherichia coli, K12. We have looked at the transcription-level response of this organism to a number of nanoparticles including the anti-bacterially important silver, metal-stress inducing ZnO and CeO2
Aims and Objectives
The genome and metabolome of E. coli are well known the system level response to nanoparticle toxicity can be studies by looking at the gene transcription response and the metabolome response over time. Three nanoparticles are studies;
- Silver – antimicrobial interactions
- ZnO – Zn2+ metal stress and photo-radical stress
- CeO2 – a nanoparticle with a persistent surface radical which leads to redox-stress.
The objectives are to look at the mechanisms of toxicity: nanoparticle dissolution and nanoparticle properties such photo-radical and redox stress.
The bacteria-nanoparticle interaction can be imaged by TEM and SEM although these images must be interpreted with care as they are 80 nm think from the microtome section with no field of view vertical resolution. So cells viewed in cross-section are the best images of the interactions. For the 15 nm particles seen here, there is no evidence that they enter the cell and they are then vectors for delivering high concentrations of nanoparticles right to the cell surface. In this interfacial region, the particles dissolve and deliver large metal doses to the cell. For low doses, the cells mount a successful adaptive stress response, for higher doses this leads to cell death.
We are looking at array transcriptome analysis of the whole genome as well as metabolome response over time course experiments to establish the nature of the response and the route to cell death.
Silver Nanoparticle enhanced Silver Ion Stress Response in Escherichia coli K12
Jonathan McQuillan1, Heidi Goenaga Infante, Emma Stokes and Andrew M. Shaw, Nanotoxicology. 2012 Dec;6:857-66.
Whole-Cell Escherichia coli-based Bio-Sensor Assay for dual Zinc Oxide Nanoparticle Toxicity Mechanisms
Jonathan Mcquillan and Andrew M. Shaw Biosensors and Bioelectronics, Available online 22 July 2013