The organisms are still aware of their surroundings even when they are dead, for the first time shown by scientists.
The bacteria could use a stored supply of charged particles for energy instead of their usual fuel to wake up.
Our understanding of how disease can spread is challenged by the discovery.
Grol Sel is a researcher from the University of California San Diego.
The ability of cells to process information was shown by us.
It is thought that one way we may encounter extraterrestrial life is in similar dormant states.
"If scientists find life on Mars or Venus, it is likely to be in a dormant state and we now know that a life form that appears to be completely immobile may still be able to think about its next steps," says Sel.
One of the key survival tactics of the bacterium is being able to shut down into spores, where they can remain in a dehydrated state for hundreds of years, despite being pretty tough.
This isn't just a nap. Thebacteria are no longer alive.
They know when it's time to wake up.
Diseases caused by the Bacillus anthracis bacterium can survive long periods without water or nutrition in the mail, if they are exposed to the right conditions.
How do they know when to awaken? If the good times don't continue for a long time, the wasted energy could be a big problem. It's possible that waiting for a feast means lost opportunities.
Sel and his team tested thousands of Bacillus subtilis spores. The longest time surviving in space is held by the bacterium, which is considered non- harmful to humans.
They measured the strength of the signals sent into the environment to see if the spores could pick them up.
It wasn't enough to have one or two of the nutrients. The cumulative effect seemed to occur over time, as thebacteria were able to keep score and switch on again after a few signals.
The team was able to observe changes in the activity of the spores in response to the short-lived signals, as well as show that thebacteria were using energy stored in the form of K +.
This is a way to store the energy for later use.
The team used a mathematical model to explain what was happening, and it showed that each signal triggered the release of potassium ion, which in turn triggered the reawakening of thebacterial flora. This model was called an integration-and-fire model.
The cumulative signal processing strategy stops thebacteria from waking up too quickly if conditions aren't quite right.
The researchers found a decision-making mechanism in inactive cells.
This is a strategy that has been used before.
Sel says that the way spores process information is similar to how our brains work.
Small and short inputs are added up to determine if a threshold has been reached. The spores return to life after reaching the threshold.
Unlike neurons, which are incredibly energy-hungry cells, the spores were able to do this without any metabolism at all.
Microbiologists Jonathan Lombardino and Briana Burton from the University of Wisconsin-Madison say that further study across other organisms known to enter a similar state, such as fungi, could help further tease out what this means for life more broadly.
Could the extreme longevity of so-called superdormant spores be traced back to their initial K+ concentrations?
There's more work to be done, but the discovery challenges our understanding of dormantbacteria as being inactive, and also changes how we view signs of extraterrestrial life in the future.
The research has appeared in a journal.
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