Analog nitrogen sensing in Escherichia coli enables high fidelity information processing

The molecular reaction networks that coordinate the response of an organism to changing environmental conditions are central for survival and reproduction. Escherchia coli employs an accurate and flexible signalling system that is capable of processing ambient nitrogen availability rapidly and with high accuracy. Carefully orchestrated post-translational modifications of PII and the glutamine synthetase allow E. coli to trace nitrogen availability in a continuous, decidedly non-digital fashion. We measure the dynamic proteomic and metabolomic responses to trace the analog computations, and use an information theoretical framework to characterize the information capacity of E. coli’ s nitrogen sensing network: we find that this system can transmit up to 9bits of information about the nitrogen state. This allows cells to respond rapidly and accurately even to small differences in metabolite concentrations.