University of Dundee

MRC DTP 4 Year PhD Programme: Cell biology of a bacterial nano-weapon. Supervisors: Dr Sarah Coulthurst (Lead); Dr Colin Rickman (2nd Supervisor), Heriot-Watt

Many bacterial pathogens use the Type VI secretion system (T6SS) nanomachine to fire diverse, toxic ‘effector’ proteins directly into target cells. It is becoming increasingly apparent that the T6SS plays a key role in the virulence and competitiveness of diverse Gram-negative bacteria, including important human pathogens. Pathogens can use T6SSs to directly target eukaryotic organisms, as classical virulence factors. Alternatively, many pathogens can use T6SSs to target other bacterial cells, killing or inhibiting rivals. ‘Anti-bacterial’ T6SSs thus provide a competitive mechanism to allow pathogens to proliferate in polymicrobial infection sites or environmental reservoirs and ultimately cause disease. Understanding how the T6SS is deployed and the lethal consequences of its effectors on targeted bacterial cells therefore offers the potential to uncover new ways to kill or inhibit bacterial pathogens.

This project aims to develop and utilise advanced fluorescence microscopy and image analysis methodologies to better understand how the T6SS is deployed and the consequences of specific effectors on targeted bacterial cells. In previous work, we have shown that the potent anti-bacterial T6SS of an opportunistic pathogen, Serratia marcescens, is deployed in an offensive manner and delivers multiple anti-bacterial toxins. Furthermore, we and others have shown that single cell microscopy approaches allow visualisation of the T6SS structure, firing events, and the subsequent impact on target cells. In this project, we will further investigate how the T6SS is deployed, using a combination of genetic, biochemical, high- and super-resolution microscopy and image analysis methods. Additionally we will elucidate the consequences of an individual T6SS-delivered anti-bacterial effector protein on the targeted bacterial cell, again by combining state-of-the-art single cell imaging with complementary genetic and molecular analyses.