  Organisms must acquire and use environmental information to guide their
behaviors. However, it is unclear whether and how information quantitatively
limits behavioral performance. Here, we relate information to behavioral
performance in Escherichia coli chemotaxis. First, we derive a theoretical
limit for the maximum achievable gradient-climbing speed given a cell's
information acquisition rate. Next, we measure cells' gradient-climbing speeds
and the rate of information acquisition by the chemotaxis pathway. We find that
E. coli make behavioral decisions with much less than the 1 bit required to
determine whether they are swimming up-gradient. However, they use this
information efficiently, performing near the theoretical limit. Thus,
information can limit organisms' performance, and sensory-motor pathways may
have evolved to efficiently use information from the environment.
