PhD Studentship: The Role of Bacterial Membrane Potential in Tuberculosis Persistence and Regrowth

This project is an industrial CASE studentship based at the Royal Veterinary College in collaboration with start-up company (Cytecom) based in Warwick. The project will investigate the biochemical, genetic, and electrophysiological pathways underlying persistent infections in tuberculosis (TB). Tuberculosis, caused by the bacterium Mycobacterium tuberculosis (Mtb), is the highest cause of mortality by a single infectious agent and kills 1.5 million people annually. Treatment of TB in humans is with lengthy, toxic, multidrug regimens and the increasing emergence of drug resistant TB is a global concern. Mtb is able to enter a physiological persistent state which is phenotypically resistant to antimicrobials.

Persistent states in many bacterial species is associated with a phenotype known as the small colony variant (SCV). The clinical importance of SCVs is highlighted by their isolation from patients with persistent, recurrent infections. SCVs show delayed growth and defects in community behaviours such as biofilm formation and cell-cell signalling. We have recently used CRISPRi to silence a putative haem synthase (HAS) in a non-pathogenic model of Mtb (Mycobacterium smegmatis) and observed a SCV phenotype. In this project we explore this phenotype using a combination of molecular microbiology, electrophysiology, and innovative mathematical modelling.

The aim of this project is to investigate persistent phenotypes in TB and measure impacts on global gene expression, membrane potential and quorum sensing behaviours. We hypothesise that silencing of the mycobacterial HAS leads to inhibition of the respiratory chain and a reduction in membrane potential. This reduction in membrane potential inhibits cell to cell communication behaviours and causes a delay in regrowth classically described in SCVs. This project will explore the novel concept that electrical signalling plays a role in allowing bacteria to sense their environment and communicate with one-another. A concept that is gaining traction in model organisms.

This project offers training in molecular microbiology such as CRISPRi gene silencing, targeted mutagenesis approaches and global transcriptomics. It offers training in mathematical modelling as neuron-firing models will be applied and modified to interpret changes in bacterial membrane potential in different physiological states.

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