Insight and interference in key weapons of bacterial competitiveness

Supervisors: Sarah Coulthurst, Ian Gilbert

Project Description
Bacteria utilise diverse strategies to attack other organisms, including rival bacteria and the host during infection. Very many of these strategies involve the deployment of different types of protein secretion system. Secretion systems are specialised machines used by bacterial cells to translocate specific proteins out of the bacterial cell and, frequently, also deliver them directly into target cells. The Type VI secretion system (T6SS) is a complex nanomachine able to 'fire' toxic effector proteins into target cells. It is increasingly appreciated as playing a key role in the virulence and competitiveness of diverse Gram-negative bacteria, including important human, animal and plant pathogens. Pathogens can use T6SSs to directly target eukaryotic host 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. These anti-bacterial T6SSs inject toxic proteins into target bacterial cells, efficiently killing them or inhibiting their growth. In the ten years since its discovery, huge strides have been made in understanding the mode of action of the T6SS. Yet, many important aspects of how this system can so efficiently deliver proteins and kill competitor bacteria remain to be elucidated. Understanding how this machine and its toxic cargo operate at a molecular level offers the exciting potential for designing strategies to both utilise and disable it for biotechnological and therapeutic purposes.

In this project, we will utilise a variety of genetic, biochemical, state-of-the-art screening and 'omic' approaches to further understand the how the T6SS achieves efficient, broad-spectrum killing of bacterial cells. In particular, we will develop high throughput assays for T6SS-dependent (and independent) anti-bacterial activity. These assays will then be used in chemical and genetic screens for molecules and genes which inhibit or enhance secretion system activity and/or bacterial killing. The mode of action of active compounds or gene products identified through screening will be then be identified using a range of approaches including cell biology, biochemistry, genetics, transcriptomics and proteomics Whilst our extensive experience of working with the T6SS will make this our initial priority, the methods that we will develop will be generally applicable to related secretion and/or inter-bacterial competition systems and we will have the option to incorporate one or more other systems into the study as progress dictates.

The project will provide research training in a broad-spectrum of molecular microbiology techniques, including molecular biology, genetic analyses, biochemical approaches and microscopy. Additionally it will offer the opportunity for training in high-throughput assay development, compound screening and optimisation. Proteomics, genomics and transcriptomics expertise is available in the host or collaborating labs as required. The student will have many opportunities to present their work at internal and external meetings and to interact with other research groups.