Physically self-organised spatial patterns in bacterial populations

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tim rudge, Fernan Federici, Paul J. Steiner, Anton Kan, Jim Haseloff

university of cambridge, United Kingdom

Synthetic biology has proved useful in both elucidating existing cellular regulatory mechanisms and constructing simple novel systems from them. A clear next step is to apply this approach to multicellular organisation. However, multicellularity is the result of a complex interplay of generative and regulatory mechanisms (cell growth, division, signaling, and genetic regulation) that are difficult to decouple. Such complexity suggests the use of simple, abstracted model systems in which each of these effects can be isolated, both for understanding them and engineering their interaction. Using layers of bacterial cells, that exhibit little or no molecular coordination of growth, we were able to effectively isolate the effects of cell shape, growth and division on the development of fluorescence-labeled cellular domains. Combining confocal microscopy, a cell-shape mutant, and computational modeling, we show that individual cell shape can cause mechanical instabilities that give rise to tissue-wide fractal patterns. We also created a simple mechanism for genetic symmetry-breaking that utilizes this effect to spontaneously generate spatial pattern – illustrating the potential for engineering.