Microbes can use self-produced molecules to coordinate their actions and perform collective tasks. We present a mathematical model to describe the mechanism driving social motility in the gram-negative bacterium M. xanthus. Our model, which was confirmed by long-term colony expansion experiments, reveals that exopolysaccharide production allows the cells to move collectively across surfaces as a coherent group. Expansion of a M. xanthus colony incubated on a nutrient agar surface for 4 days at 32°C is shown in this stereo-microscope image. Patra et al.

Image Credit: Kimberley Kissoon and Heidi B. Kaplan