*4 Year MRC PhD Programme* Cell biology of a bacterial nano-weapon

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 and populations. 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 post-translational regulation of T6SS deployment, using a combination of genetic, biochemical, high resolution and super-resolution microscopy and image analysis methods. Additionally we will elucidate the consequences of several individual T6SS-delivered anti-bacterial effector proteins on both the individual target cell and on the growth of the target population, again by combining state-of-the-art single cell imaging with complementary genetic and molecular analyses.

This project will provide research training in a broad-spectrum of molecular microbiological techniques, including molecular biology, genetic and biochemical analyses (SJC lab) and in advanced fluorescence microscopy and quantitative image analysis (JRS lab). The student will have many opportunities to present their work at internal and external meetings and to interact with other research groups.