The fluid dynamics of nascent biofilms

Dimensionality is a critical factor in how bacteria invade new areas, to access nutrients in order to propagate or to establish robust biofilms. Cells that are free to swim in three dimensions ('swimming colloids') typically perform a biased random walk governed by (population-generated) chemical gradients; those in quasi-2D liquid films on surfaces assemble into dense, spatially heterogeneous 'swarms' of transient jets and whirls. This project will investigate the influence of hydrodynamic interactions, between cells and with surfaces, on the swimming-driven density fluctuations in the transition from 3D to 2D. The student will build on the supervisors' existing research strengths and output: digital holography and theoretical development of scattering-based techniques for video microscopy. The latter is a new method that gives access to both real and imaginary components of density fluctuations in Fourier space. The length/time-dependence of this information is key to unravelling the dynamics in cooperative systems of microswimmers. The project is mostly theoretical/computational, developing hydrodynamic theory and Fourier-space image analysis, with an experimental component (<20%) implementing standard protocols. The project falls under the EPSRC theme of healthcare technologies, the cross-council initiative on anti-microbial resistance, and the grand challenge of 'Understanding the Physics of Life'.
This project will provide significant groundwork for an EPSRC programme grant, to be submitted in 2017. The proposal is a timely bridge between newly-established research groups in physics and maths. As well as the Wilson and Bees groups, the 'microswimmers' community at York has been augmented by two new lecturers in maths (Mitya Pushkin and Hermes Gadelha), in addition to the well-aligned research programmes from others - Profs. Mark Leake (physics/biology) and Seth Davis (biology), and Dr. Pegine Walrad (biology). This project will significantly advance an existing programme of research between the Wilson and Bees labs, which has so far given three peer-reviewed publications (impact factors 9.8, 7.7 and 3.8) and one patent application (LW). There are several opportunities for external impact, such as developing tools for the monitoring of transitions in biofilm pre-cursors and the rapid extraction of bacterial biased swimming characteristics.