The bacterial chemotaxis pathway - an optimal designed information processing network?

Precise adaptation of organisms to fluctuating environments is a central issue in the race of living systems for highest fitness. To this end even the simplest unicellular life forms are equipped with highly sensitive signal transduction networks. These protein networks, however, suffer from strong intercellular variations in the abundance of their components, resulting mainly from the stochastic nature of gene expression. As error-free signal transmission is obviously most desirable it can therefore be expected that effcient strategies for noise compentsation have evolved. However, as signal transduction pathways are limited in number and complexity, a cell cannot detect all environmental conditions, and the fittness of a population can be increased in certain cases by allowing cell-to-cell variations in signal respose, such that a fraction of the cell population is always highly adapted. In our reseach project we follow the question whether the E. coli chemoattractant sensing machinery follows these principles and shows the expected highly robust network design against deleterious fluctuations while simultaneously canalizing beneficial noise to achieve an optimal heterogeneous distribution of signal responses, resulting in highest possible fittness in fluctuating environments that is allowed by the given information processing mechanism.