Long-range patterns of activity shaped by signaling interactions within bacterial communities

Bacteria communicate to coordinate macro-scale patterns of gene expression and associated group behaviors such as biofilm formation. Cells secrete, sense, and respond to small chemical signals in a process known as quorum sensing. Within diverse bacterial communities, signal exchange is modulated by signaling interactions between different cell types, including interference through signal crosstalk and signal destruction. Our work explored how signaling interactions between multiple cell types shape global patterns of gene expression. We examined how community composition modulated signal-dependent gene expression using both experiments and reaction-diffusion models. In some communities, the pattern of gene expression followed a 2D percolation transition, controlled by the ratio of signal producing and signal destroying strains in the community. At a critical amount of interference, signal exchange was disrupted and long-range communication was suppressed. We explored the limitations of diffusive communication and strategies cells could use to coordinate behavior at length scales exceeding distances over which diffusion is effective.