Thermodynamic Costs of Information Processing in Sensory Adaptation
Figure 5
Energetic costs of adaptation in an E. coli chemotaxis SAS.
(A) Network representation of the nonequilibrium receptor model with five methylation and two activity states. Green arrows represent the addition/removal of methyl groups driven by the chemical fuel SAM. (B) Corresponding negative feedback topology, displaying the dissipative energy cycle (green arrow) sustained by adiabatic entropy production, due to the consumption of chemical fuel. (C) Energetics of nonequilibrium measurement in the chemotaxis pathway for a ligand concentration change of (other parameters in Materials and Methods). The instantaneous change in ligand concentration performs chemical work on the cell, which increases its free energy
as the cell responds. To adapt, the bacterium has to provide excess work
from its own chemical reservoir, the fuel SAM.