How does low-temperature plasma damage the bacterial outer membrane?

Global challenges include microbial infections, and bacterial contamination of surfaces (e.g. food) and the environment. With resistance to antibiotics an increasing concern alternative approaches need to be developed. One of these is low-temperature plasma (LTP) – formed when high voltage is applied to a gas flow. The chemical properties of atmospheric pressure LTP offers great promise as an antibiotic-free therapeutic for combating topical bacterial infection associated with wounds and skin ulcers, and are another potential weapon in our arsenal to combat antimicrobial resistance (AMR). However, there are key biological and physical questions remaining that need to be addressed to enhance the development of LTP for use in society. For example, the physical mechanism whereby the reactive species in LTP damage the bacterial envelope and render a cell non-viable is very poorly understood. To further develop and optimise the use of LTP, a greater understanding of the cellular mechanisms whereby LTP imparts its bactericidal effect is required, and this will be the focus of this project.

The project builds upon published work from previous PhD students at York [1-3], and combines our expertise in real-time single-cell fluorescence imaging (Baumann), LTP generation (O’Connell), and bacterial phenotyping across different time and length scales (van der Woude), with the goal of making significant strides forward in understanding how LTP alters the membrane bilayer both in vivo and in vitro at the single-cell level. This knowledge will feed into ongoing collaborative work involving the York Plasma Institute and the Centre for Immunology and Infection that focuses on characterising and manipulating the composition of the reactive species in plasma to enhance biological activity.

This project will investigate how different LTPs affect the cell envelope of Gram negative bacteria with different cell surfaces by using a single-cell level approach. The student will exploit methods for fluorescently-labelling different outer membrane targets to monitor morphological changes in the cell envelope during and after exposure to LTP. Time-lapse cell imaging after exposure to LTP will be done to determine if any morphological differences can be observed, and to identify potential phenotypic traits of non-viable cells and viable persister cells. Knowledge gained from this project will be used to develop a mechanistic model of LTP-induced membrane damage and identify agents that enhance the damaging effect of LTP on bacteria.

This project will provide excellent specialised training in cutting-edge single-cell analytical methods combined with membrane biology and microbiology. Professional skills training will be provided by the White Rose DTP. The student will also improve their professional skills by attending the supervisors’ lab meetings, departmental seminars and research conferences, and participating in outreach activities. The student will join a vibrant cross-disciplinary community of PhD students.

This project is suitable for an applicant with a strong background in biophysics, biochemistry, physics and/or chemistry, and a keen interest in understanding biological processes at the molecular level and participating in the development of novel antibacterial approaches.