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How dormant bacteria calculate their return to life: The thinking undead

ANI | Updated: Oct 07, 2022 11:27 IST


San Diego [US], October 7 (ANI): Some bacteria go into a dormant state where their life functions cease when exposed to hunger and stressful conditions. These cells, known as spores, can resist punishing extremes of heat, pressure, and even the harsh conditions of space by entering a profound hibernation.
Spores that may have lain dormant for years might eventually wake up and reactivate in a matter of minutes when the right circumstances arise.
Some bacteria go into a dormant state where their life functions cease when exposed to hunger and stressful conditions. These cells, known as spores, can resist punishing extremes of heat, pressure, and even the harsh conditions of space by entering a profound hibernation.
Spores that may have lain dormant for years might eventually wake up and reactivate in a matter of minutes when the right circumstances arise.
By rehydrating and resuming their physiological processes, spores awaken. But up until this point, scientists were unsure if spores could observe their surroundings while still asleep. Particularly, it was unknown how spores responded to hazy environmental cues that did not clearly denote favourable conditions. Would spores simply ignore such a diverse environment or pay attention?
Biologists from the University of California, San Diego have answered this mystery in a recent study that was published in the journal Science. Spores have a remarkable capacity to assess their environment despite remaining in a biologically dead state, according to research from the School of Biological Sciences. They discovered that spores employ electrochemical energy that has been saved, acting as a capacitor to gauge the circumstances necessary for restoration to a normal functioning life.
"This work changes the way we think about spores, which were considered to be inert objects," said Gurol Suel, a professor in the Department of Molecular Biology. "We show that cells in a deeply dormant state 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."

Numerous bacterial species use the formation of spores, which are partially dried-out cells encased in a tough protective coating, as a means of long-term dormancy. They pose a concern in the form of bacterial anthrax and contamination risk in the medical and food industries due to their extraordinary capacity.
Suel and his coworkers investigated whether latent Bacillus subtilis spores might detect transient environmental signals that were insufficient to cause them to reawaken. They discovered that spores could keep track of such minute inputs, and when the total rose above a predetermined level, they made the decision to awaken from their latent state and resume biological activity.
The researchers found that spores employ a method known as integrate-and-fire, based on fluxes of potassium ions, for evaluating the environment around them. They developed a mathematical model to assist explain the process. They discovered that spores responded to favourable signals, even those that were fleeting and insufficient to cause an emergence from hibernation.
Instead of waking up, spores responded to each minor input by releasing some of their potassium reserves. They then added up successively positive signals to decide whether the environment was conducive for exiting. Such a cumulative signal processing approach enables the detection of favourable external conditions and prevents spores from "jumping the gun" into an unfavourable environment.
Spores process information similarly to how neurons do in our brains, according to Suel. "Small and brief inputs are piled up over time in both bacteria and neurons to assess whether a threshold is achieved. As soon as the threshold is crossed, the spores begin to revive, and the neurons begin to discharge action potentials to communicate with one another. It's interesting to note that whereas neurons are among our bodies' most energy-dependent cells, spores can carry out this signal integration without utilising any metabolic energy.
The new knowledge about spores, according to the researchers, reframes commonly held beliefs about cells that appear to be dead and are in an exceedingly inactive state. These discoveries have ramifications for assessing the presence of life on meteorites and in space missions looking for signs of life.
"This work suggests alternate ways to cope with the potential threat posed by pathogenic spores and has implications for what to expect from extraterrestrial life," said Suel, who holds affiliations with the San Diego Center for Systems Biology, BioCircuits Institute and Center for Microbiome Innovation. "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 inert may still be capable of thinking about its next steps." (ANI)

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