Unravelling how bacteria use pili-based motility in biofilms

Most bacteria live in densely packed assemblages called biofilms. Cells in these communities use tiny grappling hooks called pili to pull themselves across surfaces. This project aims to study how rod-shaped bacteria collectively migrate across a surface using pili. When these cells are packed together at high density, the motility of neighbouring cells tends to align with one another, creating larger scale patterns of flow with an appearance similar to turbulence. This project aims to understand how different genotypes of bacteria, which move at different speeds and have different lengths, compete when they are mixed together within biofilms. Using a combination of new massively cell tracking algorithms and genetically engineered bacteria, we plan to measure how individual cells modify their movement behaviour in a biofilm to efficiently spread across a surface as a collective. To support our experiments, we will build both individual based and continuum models that will explain how topological defects (points where cells with different orientations meet each other) interact within an expanding biofilm. We will use theory originally developed to study topological defects in liquid crystals as the basis for our modelling efforts.

Our study will analyse the behaviour of Pseudomonas aeruginosa, an opportunistic pathogen and major cause of infection in vulnerable patients, including burn victims and carriers of cystic fibrosis (CF). Recently, the World Health Organisation named P. aeruginosa as one of three bacterial species in greatest need of R&D for new antibiotic development. The combined experimental and modelling programme carried out by the student will elucidate the fundamental physics and molecular systems that bacterial communities use to proliferate and spread. This work, thus, may ultimately yield new targets for antimicrobial therapies that will allow us to disrupt the spread of biofilm infections in clinical settings. This highly interdisciplinary project falls both within EPSRC priority areas "New physical sciences for biology and healthcare" and "Fluid dynamics".