Mathematical modelling and sensitivity analysis of the signal transduction pathway underlying chemotaxis in Escherichia coli suggests a mechanism for high sensitivity over a dynamic range of five orders of magnitude. The analysis reveals that the enhancement in sensing ability occurs in the signal receiving module that is comprised of ligand binding, change of occupancy and change of receptor activities. The clustering of receptors contributes to the signal capability by exploiting interactions between receptors for the activity change. The role of the autophosphorylation of the histidine kinase CheA and the phosphotransfer to the response regulator protein CheY is to relay the signal to the cell's motor apparatus at little expense to the sensitivity at low stimuli. The results also provide insight on the values of kinetic parameters that maximise the efficiency of the signalling pathway.