When conditions get a little too extreme, some bacteria are able to lock themselves into a dormant state where their life processes stop.
These “dead” cells, called spores, can withstand enormous stresses while in this state, including extreme heat, pressure, and even the harsh conditions of space, and can remain so for thousands of years.
Then, when conditions become favorable again, spores that have lain dormant for years can wake up and spring back to life in minutes – like a zombie rising from the grave.
Now scientists know that these bacterial spores have the extraordinary ability to assess their environment while remaining in this physiologically dead state, according to new research published in Science.
They found that the spores gradually release stored electrochemical energy, and this allows them to calculate when the time is right to resume normal biological activity – even when environmental signals are vague and do not clearly indicate favorable conditions.
“This work changes the way we think about spores, which were considered inert objects,” says Gürol Süel, a professor in the Department of Molecular Biology at the University of California, San Diego in the US.
“We show that cells in deep dormancy have the ability to process information.
“We discovered that spores can release their stored electrochemical potential energy to perform a computation about their environment without the need for metabolic activity.”
Many species of bacteria form spores – partially dehydrated cells surrounded by an elastic protective coating – one of the most notorious creatures Bacillus anthracisthe spores of the bacterium that cause Anthrax.
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Use of mathematical model and experiments with aggregates Bacillus subtilis spores, Süel and his colleagues were able to determine that the bacteria were able to sense and measure short-lived environmental signals too weak to trigger a return to life on their own.
They do this by releasing some of their stored potassium in response to each small input until a critical threshold is reached, turning the spores into an active state.
“The way the spores process information is similar to the way the neurons in our brain work,” says Süel. “In both bacteria and neurons, small and brief inputs add up over time to determine whether a threshold is reached.
“Upon reaching the threshold, the spores begin their return to life, while the neurons fire an action potential to communicate with other neurons.”
This finding has implications for the search for evidence of life beyond Earth.
“This work suggests alternative ways of dealing with the potential threat posed by pathogenic spores and has implications for what to expect from alien life,” says Süel.
“If scientists find life on Mars or Venus, it’s likely to be in a dormant state, and now we know that a life form that appears to be completely dormant may still be able to think about its next steps.”