Cyanobacteria use a principle similar to AM radio to coordinate cell division with circadian rhythms by encoding information through pulse amplitude modulation. Cyanobacteria, an ancient group of photosynthetic bacteria, have been found to regulate their genes using the same physical principle used in AM radio transmission.

A new study has been published Current Biology, found that cyanobacteria use changes in the amplitude (strength) of the pulse to transmit information within individual cells. This discovery sheds light on how biological rhythms work together to regulate cellular processes.

In AM (amplitude modulation) radio, a wave of constant power and frequency, called the carrier, is produced by oscillating electric current. An audio signal containing the information to be transmitted (such as music or speech) is superimposed on the carrier wave. This is done by changing the amplitude of the carrier wave according to the frequency of the audio signal.

A research team led by Professor James Locke from the Sainsbury Laboratory at the University of Cambridge (SLCU) and Dr Bruno Martins from the University of Warwick has discovered that a mechanism similar to AM radio is at work in cyanobacteria.

In cyanobacteria, the cell division cycle, in which a cell grows and divides into two new cells, acts as a “signal carrier.” The modulation signal then comes from the bacterium’s 24-hour circadian clock, which acts as an internal timekeeping mechanism.

Solving the ancient cellular puzzle

This discovery answers a long-standing question in cell biology: How do cells integrate signals from two oscillatory processes—the cell cycle and circadian rhythm—that operate at different frequencies? Until now it was unclear how these two cycles could be coordinated.

To solve the puzzle, the research team used single-cell time-lapse microscopy and mathematical modelling. They monitored the expression of the alternative sigma factor RpoD4 protein using time-lapse microscopy. RPoD4 plays an important role in initiating transcription, the process by which genetic information from DNA is copied into RNA. The simulations allowed the researchers to study signal processing mechanisms by comparing simulation results with microscopy data. The team discovered that RpoD4 only activates pulses that occur during cell division, making it an ideal candidate to monitor.

Lead author Dr. Chao Ye explained: “We found that the circadian clock determines how strong these impulses are over time. Using this strategy, cells can encode information about two oscillatory signals in a single output: cell cycle information at pulse frequency and 24-hour clock information at pulse strength. “This is the first time we have observed a circadian clock that uses pulse amplitude modulation, a concept often associated with communications technology, to control biological functions.”

consequences of results

“Changing the frequency of the cell cycle due to ambient light, or the circadian clock due to genetic mutations, confirmed the basic principle. “It is surprising to see examples in the nature of what we sometimes think of as ‘our’ engineering rules,” said co-author Dr Martins. “A cyanobacterial lineage 2.7 billion years ago has evolved and provides an elegant solution to this information processing problem.”

Professor Locke added: “One of the reasons we are studying cyanobacteria is that they have the simplest circadian clock of any organism, so understanding this lays the foundation for understanding clocks in more complex organisms such as humans and agricultural crops.

“These principles could have broader implications in synthetic biology and biotechnology. For example, they could help us grow crops that are more resilient to changing environmental conditions, and this could have implications for agriculture and sustainable development.”