Bacterial Quorum Sensing Allows Graded and Bimodal Cellular Responses to Variations in Population Density
Jennifer B. Rattray, Stephen A. Thomas, Yifei Wang, Evgeniya Molotkova, James Gurney, John Varga, Sam P. Brown
Abstract
Bacteria can be highly social, controlling collective behaviors via cell-cell communication mechanisms known as quorum sensing (QS). QS is now a large research field, yet a basic question remains unanswered: what is the environmental resolution of QS? The notion of a threshold, or "quorum," separating coordinated ON and OFF states is a central dogma in QS, but recent studies have shown heterogeneous responses at a single cell scale. Using Pseudomonas aeruginosa, we showed that populations generate graded responses to environmental variation through shifts in the proportion of cells responding and the intensity of responses. In an infection context, our results indicate that there is not a hard threshold separating a quorate "attack" mode and a subquorate "stealth" mode.