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> The biochemistry of how they work; new research:
> 
> https://phys.org/news/2022-10-undead-dormant-bacteria-life.html
> 
> "Facing starvation and stress conditions, some bacteria enter a dormant state in which life processes stop. Shutting down into a deep dormancy allows these cells, called spores, to withstand punishing extremes of heat, pressure and even the harsh conditions of outer space.
> 
> "Eventually, when conditions become favorable, spores that may have been dormant for years can wake up in minutes and spring back to life.
> 
> "Spores wake up by re-hydrating and restarting their metabolism and physiology. But until now scientists did not know whether spores can monitor their environment "in their sleep" without waking up. In particular it was not known how spores deal with vague environmental signals that do not indicate clearly favorable conditions. Would spores just ignore such mixed conditions or take note?
> 
> ***
> 
> "They found that spores use stored electrochemical energy, acting like a capacitor, to determine whether conditions are suitable for a return to normal functioning life.
> 
> ***
> 
> "Süel and his colleagues tested whether dormant Bacillus subtilis spores could sense short-lived environmental signals that were not strong enough to trigger a return to life. They found that spores were able to count such small inputs and if the sum reached a certain threshold, they would decide to exit the dormant state and resume biological activity.
> 
> "Developing a mathematical model to help explain the process, the researchers discovered that spores use a mechanism known as integrate-and-fire, based on fluxes of potassium ions for appraising the surrounding environment. They found that spores responded to even short-lived favorable signals that were not enough to trigger an exit from dormancy. Instead of waking up, spores released some of their stored potassium in response to each small input and then summed consecutive favorable signals to determine if conditions were suitable for exiting. Such a cumulative signal processing strategy can reveal whether external conditions are indeed favorable, and prevents spores from "jumping the gun" into a world of unfavorable conditions.
> 
> "'The way spores process information is similar to how neurons operate in our brain," said Süel. "In both bacteria and neurons, small and short inputs are added up over time to determine if a threshold is reached. Upon reaching the threshold spores initiate their return to life, while neurons fire an action potential to communicate with other neurons." Interestingly, spores can perform this signal integration without requiring any metabolic energy, while neurons are among the most energy-dependent cells in our bodies."
> 
> Comment: did this develop in natural evolution by trial and error?  A highly complex mechanism of this sort imitating neurons demands it be designed. It is by definition, irreducibly complex.