Microorganisms have colorful social lives. They become aware of each other’s presence through quorum signals; they form alliances against common enemies; they find strength in numbers, collectively secreting digestive enzymes, iron scavengers, or scaffolding proteins. There is great variability in social behavior not only across species but also within individual microbes. Some work selflessly towards the common good, whereas others free ride.

The secreted cooperative factors and toxins will almost always travel through an aqueous medium before reaching and affecting another individual’s fitness. Thus, it is natural to hypothesize that the diffusive and fluid dynamical properties of the medium should be an important determinant of species' social nature.

In the conceptual cover art of the February 6 issue of Biophysical Journal, and in our computational study, we envision a future in which it is possible to fine-tune the social behavior of microbes by modulating the fluid environment in between them. In this vision, flow patterns, flow domain geometry, and carefully timed external chemical inputs are the means to steer social evolution. The circuit elements of "evolutionary engineering" are vortex chambers that separate and localize selfish and altruistic microbes, microfluidic arrays that filter out cheaters and leave behind cooperators, and carefully timed and dosed drug pulses providing the best evolutionary stage for the desired social behavior.

Our group models systems at the interface of physics, ecology, and evolution. To learn more, visit our website.

 — Gurdip Uppal and Dervis Can Vural