Frequency-dependent Chemotactic Target Selection

Chemotaxis usually involves cellular motion towards an exogenous, often static, source of chemoattractant. We demonstrate an enhanced mechanism in which a single particle (the cell) releases a chemical that diffuses to fixed particles (targets) and signals the production of another chemical by the targets. This secondary chemical acts as the cell’s chemoattractant. To reach a single target, we describe optimal strategies that arise for the release of a fixed amount of probe chemical. In the presence of multiple targets, the one selected by the cell depends on the strength and, more interestingly, the frequency of probe chemical release. Although it involves one more step than standard chemotaxis, our simple chemical “pinging” mechanism can offer far greater flexibility in regulating target selection seen in a number of physical or biological realizations.