This simple, generic biological integral-control component is used by E. coli to decide on an adaptive tumbling frequency.

1. If Ligand concentration stays constant, the bacterium tumbles at a low, exploratory rate of ~2 Hz.

2. If Ligand concentration rises (attractant), tumbling frequency falls to continue moving toward the source.

3. If Ligand concentration falls (repellant), tumbling frequency rises to avoid the source.