Soft Matter and Complex Systems Seminar

Biofilms – surface-attached bacterial conglomerates – are not only ubiquitous in nature but also play a major role in industry and medicine, where biofilm growth on implants and catheters, and the evolution of antibiotic resistance is a concern. In the last ten years, thanks to the work of researchers from the soft-matter and statistical physics community (including our group), we have learned that mechanical interactions between bacterial cells and the surface on which they grow affect the shape of bacterial colonies [1,2] and population dynamics of novel genetic variants (mutations) in such colonies. This has been mostly investigated in bacterial colonies grown on agarose gel. When a colony is initiated with a mixture of two different fluorescent microbial strains, radial expansion and random fluctuations in the number of bacteria at the edge of the colony lead to the formation of “sectors” of genetically related bacteria. In this presentation, I will focus on how cell shape, cell-cell and cell-substrate adhesion and friction affect the probability that a faster-growing mutant ‘surfs’ at the colony’s frontier and creates a macroscopic sector. Although all these physical factors contribute to the surfing probability in seemingly different ways, I will show that they do it by affecting two key parameters that in turn influence the surfing probability: front roughness and cell alignment. These properties can be modified by chemical compounds that affect the bacteria and/or the surface, as well as by patterning the surface in a special way. Our work suggests a possible new approach to fighting persistent biofilms: the physical properties of bacterial cells could be targeted alongside standard antimicrobial therapy to kill the bacteria while at the same time reducing the probability of evolving resistance to antibiotics.

References:
[1] F. D. C. Farrell, O. Hallatschek, D. Marenduzzo, and B. Waclaw, Physical Review Letters 111, (2013).
[2] M. A. A. Grant, B. Waclaw, R. J. Allen, and P. Cicuta, Journal of The Royal Society Interface 11, 20140400 (2014).
[3] M. Gralka, F. Stiewe, F. Farrell, W. Möbius, B. Waclaw, and O. Hallatschek, Ecology Letters 19, 889 (2016).
[4] F. D. Farrell, M. Gralka, O. Hallatschek, and B. Waclaw, Journal of The Royal Society Interface 14, 20170073 (2017).
[5] C. Watson, P. Hush, J. Williams, A. Dawson, N. Ojkic, S. Titmuss, and B. Waclaw, EPL 123, 68001 (2018).