Shape, shear, search & strife; mathematical models of bacteria

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This project aims to develop an integrated mathematical model to explore the early stages of bacterial biofilm formation. The project requires the development of new mathematical models that can correctly capture details of how bacteria move in fluid environments and colonize surfaces. Furthermore, recent experiments on surface-attached bacteria have identified new movement patterns that are not currently captured in existing mathematical models. We will, therefore, be undertaking mathematical research to tackle the important societal and economic challenge of biofilms. The resulting new mathematical models and techniques will also be of relevance to many other phenomena concerning active particles that can transition between existing in the bulk fluid and being attached to a surface. Bacteria are among the most primitive forms of life. Yet, despite their relative simplicity and small size, bacteria can actively sense a remarkable diversity of different environmental signals, and use this information to direct their motility towards more favourable environments. This ability to move profoundly affects where we expect to find bacteria. It is important to study biofilms because during bacterial infection the emergence of anti-microbial resistance frequently occurs within biofilms; and combatting bacterial infections in a major health challenge. Furthermore biofilms have impact beyond health: a study by the National Biofilm Innovation Centre estimated that biofilms act on a $4 trillion global industrial base operating across many sectors, including contamination of food and water supplies, disruption of oil and gas and biofouling in marine environments, and also benefitting waste-water treatment processes, biorefining and biotechnology.Many factors affect how biofilms form. In this project we focus on the very early stages of biofilm formation where the behaviour of cells, in particular the way in which they move and compete with each other, can profoundly impact what happens in the later stages. By developing a mathematical framework, we will clarify the complexity of the problem, and be able to test biological hypothesis concerning how different bacterial species compete and colonize surfaces. The ability of bacteria to swim and move up chemical gradients (chemotaxis) has been well-known for several decades. However we still cannot fully predict where the bacteria are, and how likely they are to encounter a surface, in flow environments such as the digestive tract or circulatory system. This is the challenge we address in our first objective (shape & shear). It has recently been discovered that some surface-attached bacteria can undergo chemotaxis, and our second objective (search) aims to develop a new model to explain the mechanisms for this and develop a model which can predict where bacteria will accumulate on a surface. Our final objective (strife) will investigate how bacterial strains with different growth and motility signatures compete, either indirectly through competition for resources, or directly for example through toxin production. By developing a mathematical model of this we can investigate the early spatial patterning of bacteria on a surface, which will impact the composition of resultant biofilms.