Self tuned criticality amplifies signals in bacterial chemotaxis*

Many sensory systems must amplify weak signals that arrive at single receptors. One method to achieve such sensitivity is to embed receptors into a larger system tuned close to a critical point, such that small changes to input signal are amplified into a large change in output behavior. Here, we propose a model where chemoreceptors act as the edges for the percolation of activity between signaling proteins. This system achieves high amplification by exploiting the diverging susceptibility found near the percolation transition. Output from the signaling proteins is fed back into the system to drive it towards criticality and maintain amplification over a wide range of input signals. Our model provides a mechanistic explanation of the high signal amplification at the cost of large noise which occurs in E. coli chemotaxis signaling.