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Imaging evolved multicellular behaviour of bacterial colonies during plant infection

Principal Supervisor: Professor Murray Grant, School of Life Sciences 

Co-supervisor: Professor Lorenzo Frigerio, School of Life Sciences

PhD project title: Imaging evolved multicellular behaviour of bacterial colonies during plant infection

University of Registration: University of Warwick

Project outline:

Bacterial diseases of plants are increasing alarmingly across Europe, USA and Africa, threating food security. The UK landscape is being changed by bacterial infections of oak and horse chestnut trees. Unlike fungal pathogens there is currently no effective control measures.

Our knowledge of plant defence mechanisms has improved dramatically, but we don’t understand how successful pathogens grow. Understanding bacteria disease dynamics and colony establishment will provide answers to many fundamental questions about how bacterial infections establish as well opening up opportunities for new intervention strategies.

This project combines state-of-the-art imaging, microbiological and genetic approaches to address how a successful single bacterial pathogen evolves into a distinct community within the plant apoplast; in other words the sociobiology of bacteria.

The candidate will have the opportunity push technological boundaries in imaging to understand the inter-relationship between homogeneous and heterogeneous bacteria and their respective roles within and between different community’s.

The project will use the model bacterial plant pathogen, Pseudomonas syringae and the model plant, Arabidopsis thaliana. Thus, a rich resource of biological tools lie at the candidate’s disposal. Ideally, we want to dissect how a single bacterial cell evolves different roles in ensuring community integrity and functioning. The bacteria which successfully suppresses defence rapidly multiplies (Fig. 1), but these colonies as they “talk” to each other and individuals take over new roles as they share workload and community goods (depicted in Fig. 2). Remarkably, our understanding of how these bacterial colonies form in the apoplast is virtually non-existent.

pic 2

This project will combine scanning and confocal microscopy of a novel bacterial line carrying multiple reporter genes to quantify and describe the following; (i) how colonies form, (ii) whether colony composition is static or internally dynamic, (iii) how bacterial populations within colonies co-operate and distribute workload, and (iv) how communities evolve to be spatially distinct. This will be achieved using virulent P. syringae strains with multiple reporter constructs (see Fig. 2) recording effector delivery (virulence; pink cells), quorum sensing (purple-blue cells) or public goods catabolism (both carbohydrate and nitrogen; green cells). These reporters will serve to both map population dynamics in the colonies and enable reconstruction of metabolic virulence strategies, which may help identify agrochemical targets.

Subsequently, studies will be extended to capture and model a range of heterogeneous colony dynamics and composition using mixed infections.

BBSRC Strategic Research Priority: Food Security

Techniques that will be undertaken during the project:

The candidate will receive a very broad grounding in a range of techniques while exploring this novel area of research. Skills that will be developed include core skills in scanning and confocal microscopy, plant pathology, basic molecular cloning, microbiology, plant husbandry image acquisition, cell sorting, transcriptomics, colony data analysis and modelling (colony growth and spatial distribution within colonies).

While a reporter strain will be provided, it is expected the candidate will modify/refine this as the project develops thus developing skills in gene-knockouts in bacteria..

A range of plant mutants with altered responses to Pseudomonas infection and a wealth of microarray data on the host response to the infection process itself underpin the project, thus providing training in reverse genetics and big data analysis.

Contact: Professor Murray Grant, Scool of Life Sciences