Abstract: Bacteria in biofilms use grappling hook like appendages called pili to pull themselves across surfaces and past one another. This talk will discuss two projects that illustrate how Pseudomonas aeruginosa cells use pili to obtain a competitive advantage in biofilms. First, I will discuss how we used microfluidic devices and massively parallel cell tracking to demonstrate that single cells can selectively deploy pili from the side of their bodies directed towards larger concentrations of nutrients. We find this behavior generates chemotaxis, which allows them to navigate towards the source of nutrients with remarkable submicron precision. Second, I will discuss how cells densely packed together use pili to collectively migrate across a surface. Interestingly, we find genotypes that individually move slower can collectively migrate faster as a group. Using both cell tracking and theory originally developed to study liquid crystals, we resolve the physical basis underlying this observation: bacteria moving faster than a fundamental ‘speed limit’ are preferentially reoriented perpendicular to the surface, which traps them where nutrients are scarce. This finding suggests biofilms select for cells that individually move slower, which ensures efficient movement as a collective. Taken together, our work reveals how pili-based motility shapes biofilm communities and potentially offers new tools to manipulate them to our advantage.
William ‘Mack’ Durham graduated with a BS in Civil Engineering from Clemson University in 2004. He then moved to MIT where he initially worked on ocean wave mechanics, receiving a SM in 2006. His interests then shifted to microbiology and he completed his PhD at MIT in 2012 on interaction between phytoplankton motility and fluid flow. After his PhD, Mack moved to the University of Oxford where he worked for four years as a lecturer in the Department of Zoology. In 2016, he moved to his current position in the Department of Physics and Astronomy at the University of Sheffield. His group uses a wide diversity of tools, including molecular biology, microfluidic experiments, automated cell tracking, and mathematical modelling to understand the mechanisms that cells use to exploit their microscale environment and each other.
The Durham Lab Website: