Bacteria often live in communities, where they can cooperate and also compete with each other for resources. It remains unclear how these opposing interactions are resolved at the population level. We investigated such conflicts within Bacillus subtilis biofilm communities. In part I, I will show how a biofilm resolve internal conflict. Cells at biofilm periphery not only protect interior cells from external attack, but also starve them through nutrient consumption. We discovered that this conflict between protection and starvation is resolved through emergence of long-range metabolic codependence between peripheral and interior cells. As a result, biofilm growth halts periodically, increasing nutrient availability for the sheltered interior cells. We show that this collective oscillation in biofilm growth benefits the community in the event of a chemical attack. In part II, I will show how distant biofilms resolve external conflict. We discovered that two biofilms undergoing growth oscillations become coupled through electrical signaling and synchronize their growth dynamics. Coupling increases competition by also synchronizing demand for limited nutrients. We show that biofilms resolve this conflict by switching from in-phase to anti-phase oscillations. This results in time-sharing behavior where each community takes turns consuming nutrients, which enables biofilms to counterintuitively increase growth under reduced nutrient supply. These findings indicate that bacterial communities can coordinate their dynamics to resolve competing metabolic demands in space and time, suggesting new strategies for biofilm control.
Coffee: 3:30 pm, 245 Compton