Bacterial chemotaxis is one of the most thoroughly studied signaling systems in biology. We are interested in understanding the properties of Escherichia coli chemotaxis as an example of evolutionary optimized system, which has been selected for such properties as high sensitivity, signal integration, rapid response and robustness. We are further making use of the plasticity of the chemotaxis system to design sensitive and versatile biosensors that can detect a wide range of chemical compounds.