Organisms acquire and use information from their environment to guide their behaviour. However, it is unclear whether this information quantitatively limits their performance at behavioural tasks. Here we relate information to the ability of Escherichia coli to navigate up chemical gradients, the behaviour known as chemotaxis. First, we derive a theoretical limit on the speed with which cells climb gradients, given the rate at which they acquire information. Next, we measure cells’ gradient-climbing speeds and the rate of information acquisition by their chemotaxis signalling pathway. We find that E. coli cells make behavioural decisions with much less than the one bit required to determine whether they are swimming up the gradient. Some of this information is irrelevant to gradient climbing, and some is lost in communication to behaviour. Despite these limitations, E. coli cells climb gradients at speeds within a factor of two of the theoretical bound. Thus, information can limit the performance of an organism, and sensory–motor pathways may have evolved to efficiently use information acquired from the environment.

生物体从环境中获取并使用信息来指导其行为。然而，尚不清楚这些信息是否在数量上限制了他们在行为任务中的表现。在这里，我们将信息与大肠杆菌向上化学梯度导航的能力联系起来，这种行为称为趋化性。首先，考虑到细胞获取信息的速率，我们得出了细胞爬升梯度速度的理论极限。接下来，我们测量细胞的梯度攀爬速度和趋化信号通路的信息获取速率。我们发现，大肠杆菌细胞做出行为决策所需的比特数远少于确定它们是否沿梯度游动所需的比特数。其中一些信息与梯度攀登无关，而另一些则在与行为的沟通中丢失。尽管有这些限制，大肠杆菌细胞爬升梯度的速度在理论界限的两倍之内。因此，信息可以限制有机体的性能，而感觉运动通路可能已经进化到可以有效地利用从环境中获取的信息。