8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.19Spatial structure in two dimensions for growing bacterialpopulationsDiarmuid Lloyd, 1 Paul Clegg, 1 and Rosalind Allen 11 The University of Edinburgh, SUPA, School of Physics and Astronomy, University ofEdinburgh, Mayfield Road EH9 3JZ, Edinburgh, United KingdomIn spatially structured geometries such as small cavities or surfaces, bacterial populations growrapidly from single cells to form densely packed self-assembled structures. The complex organisationof these communities is biologically important, since they must be compact enough to provideprotection from harmful environmental factors while remaining open enough to allow flow of nutrientsand waste. These self-assembled structures also have many interesting physical properties,including nematic ordering of rod-shaped cells, buckling and streaming instabilities, and geneticsegregation due to birth-death fluctuations at expanding population fronts. We present an experimentalstudy of the complex spatio-temporal organisation which arises when Escherichia colibacteria colonise a surface. Using time-lapse fluorescence microscopy, we follow the developmentof spatial order as individual cells distributed across a flat surface grow into microcolonies, whichsoon have to compete for space with the advancing population fronts of neighboring colonies. Westudy both the dynamics of the interfaces between local regions of proliferating cells and the patternsof genetic segregation that arise once the bacteria have fully populated the surface. Thesepatterns are analysed using techniques familiar from structural analysis in soft matter physics: ourresults show that highly non-trivial structures emerge from the interplay between growth, localnematic ordering and competition for space.19