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Buckling instabilities in chaining bacterial colonies

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If you have a question about this talk, please contact Fulvio Forni.

Bacteria frequently grow together as colonies. Large, complex colonies, known as `biofilms’, are often multi-species and exhibit cooperative behaviour reminiscent of multicellular organisms, such as signalling and controlled cell death. However, even at the early stages, colonies exhibit many different structures and morphologies, which are controlled by a dynamic interplay between cell growth and division, the shape of cells and the physical interactions between them. One type of interaction, called `chaining’, consists of the maintenance of a physical, usually protein, link between sister cells following division. Chaining is common in many bacterial species, but is particularly well known in the rod-shaped Bacillus subtilis, where buckling of single chains of bacteria leads to convoluted, open colonies with many pores and channels. This contrasts with the structure of non-chaining bacteria, such as Escherichia coli, which typically fracture into multiple small, aligned domains. Here, I will present 2D discrete-element simulations of growing bacterial colonies, where we continuously tune the probability and strength of chaining between daughter cells. At the extremes, we reproduce the behaviour of B. subtilis and E. coli -like colonies, but for intermediate values of the chaining parameters, we identify a novel state, where the whole colony buckles collectively. A toy, lattice model reproduces the shape of the transition between the `aligned domains’ and `collective buckling’ states, and enables us to show that the impact of chaining is to modify the rate and probability with which these different mechanisms occur.

The seminar will be held in LR4 , Baker Building, Department of Engineering, and online (zoom):

This talk is part of the CUED Control Group Seminars series.

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