pnas | Cells often perform computations in order to respond to environmental
cues. A simple example is the classic problem, first
considered by Berg and Purcell, of
determining the concentration of a chemical ligand in the surrounding
media. On general
theoretical grounds, it is expected that
such computations require cells to consume energy. In particular,
Landauer’s principle
states that energy must be consumed in
order to erase the memory of past observations. Here, we explicitly
calculate the energetic
cost of steady-state computation of ligand
concentration for a simple two-component cellular network that
implements a noisy
version of the Berg–Purcell strategy. We
show that learning about external concentrations necessitates the
breaking of detailed
balance and consumption of energy, with
greater learning requiring more energy. Our calculations suggest that
the energetic
costs of cellular computation may be an
important constraint on networks designed to function in resource poor
environments,
such as the spore germination networks of
bacteria.
