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). A mix of biologically active reactive oxygen
and nitrogen species are 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 (e.g. Are pores formed in the
membrane?). To further develop and optimise the use of LTP, a greater
understanding of the cellular mechanisms of its bactericidal effects is required,
and this will be the focus of this project.
Our current understanding of how LTP affects microbes is largely based on
population-level cell viability assays or single-cell imaging techniques with poor
temporal resolution due to the need for extensive sample preparation prior to
imaging. By combining our expertise in real-time single-cell fluorescence
imaging (CGB), LTP generation (DO'C), and bacterial phenotyping across
different time and length scales (MvdW), significant strides forward can be
made in understanding how plasma treatment alters the membrane bilayer
both in vivo and in vitro. This knowledge will feed into ongoing work in the York
Plasma Institute 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 bacterial strains with different cell surfaces by using a single-cell level
approach. The student will exploit methods for fluorescently-labelling OMPs
and LPS to monitor morphological changes in the cell envelope during and after
exposure to LTP. Single-cell imaging will be done using advanced multi-colour
fluorescence microscopy methods and novel technology developed to allow
simultaneous exposure to different types and dosages of 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 potential agents that could be used to enhance the damaging effect of
plasma on Gram negative bacteria.
This project will provide excellent specialised training in cutting-edge single-cell
analytical methods combined with a good understanding of 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 physics and
chemistry, and a keen interest in understanding biological processes at the
molecular level and participating in the development of novel antibacterial
approaches.