Effects of cell-cell communication on bacterial chemotaxis

Bacteria track chemical gradients using a biased random walk, a process called chemotaxis. Experiments suggest that bacteria also communicate during this process. Using a mathematical model, we find that sufficiently strong communication succeeds in keeping a population of bacteria together but slows down chemotaxis. However, if the secretion of the communication molecule is coupled to the detection of the external chemoattractant, chemotaxis can be faster than without communication. This result assumes that cells can detect and subtract the average of the chemoattractant over the population, a mechanism we term adaptive communication. Intriguingly, in this regime we predict that, even though blocking the communication receptors should slow down chemotaxis, overexpressing them should also slow it down, and partially blocking or underexpressing them may actually speed it up. Our work provides physical insights on how communication and chemotaxis are connected and may help explain why chemotaxing bacteria communicate.