Effective bacterial aggregation is achieved by partial disassembly

Biofilm engineering is a promising field with many environmental, medical, industrial, and scientific applications, which requires understanding and control of biofilm properties. Here we study a system of suspended bacteria expressing blue-light-sensitive adhesive proteins on their membranes. Experiments show that the aggregation of the bacteria is more efficient and yields bigger clusters under pulsed-light-illumination than when they are exposed to constant blue light. To understand how this occurs, we used an individual-based-model of the bacteria as spherocylindrical particles with switchable adhesion. We chose the parameters of the adhesive forces by fitting to earlier experiments. With the decay rate of the adhesive force as the only fit parameter, we can quantitatively recreate the experimental results. We thus find that the dynamics of the aggregation are controlled by the interplay between the time scale of cluster disassembly and the length of the periods of darkness in between pulses of light.