Quantifying second-messenger information transmission in bacteria

Bacterial second messengers are crucial for transmitting environmental information to cells. However, quantifying their information transmission capacity remains challenging. Here we develop a framework for quantifying information processing in cellular signalling systems. We engineer an isolated cyclic adenosine monophosphate (cAMP) signalling channel in Pseudomonas aeruginosa using targeted gene knockouts, optogenetics and a fluorescent cAMP probe. This design enables precise optical control and real-time monitoring of cAMP dynamics. By integrating experimental data with information theory, we reveal the optimal frequency for light-mediated cAMP signalling that maximizes information transmission, reaching about 40 bits per hour. This rate correlates strongly with cAMP degradation kinetics and uses a two-state encoding scheme. Our findings suggest a mechanism for fine-tuned regulation of multiple genes through temporal encoding of second-messenger signals, providing insights into bacterial adaptation strategies.