The ultimate secret of "coming back from the dead", Science has finally discovered how bacteria wake up their sleeping slumbers

▎WuXi AppTec content team editor

When extreme environments arrive and are no longer suitable for survival and reproduction, bacteria will transform into the form of
spores.
This transition allows bacteria to gain superior resistance, and spores can tolerate extreme dryness, temperature and pressure, such as some pathogenic bacteria that can remain in the soil for years after transforming into spores, and will wake up
again when the environment is right.

But scientists have long believed that spores are in a very vague state of life, strictly speaking, spores do not undergo deep sleep like hibernating animals, they are physiologically no different from death, because the spores do not have any metabolic activity
.

Image source: 123RF

But surprisingly, such a dead spore can know when to wake up, and as long as the time is right, the bacteria can resurrect and multiply and expand the army
.
This process has also fascinated
many microbiologists.

Recently, a new study in Science for the first time discovered the small mystery of spores "coming back from the dead", although they are not metabolized, they can be adjusted with the help of charged particles stored inside, and according to the small changes in the particles, they tell themselves the level of nutrition in the outside world, so as to decide whether to wake up
.

"This study has changed the way we think about bacterial spores, which we used to think of as extremely indolent objects," says Professor Gürol Süel, a molecular biologist at the University of California, San Diego, adding that spores still retain the ability to process information, especially using electrochemical potential energy to "calculate" the nutritional changes around them, a process that does not require metabolic involvement
at all.

The new study tracked thousands of spore states of Bacillus subtilis in real time, which are so survivable that they can even survive stress tests in space for a long time
.

Very brief pulses of nutrients were given in their environment, and a single nutritional signal was not enough to directly revive
the spores.
According to the author's follow-up observations, the previous few nutritional pulses did seem to have nothing to happen, and the spores were still lifeless
.

The stronger the nutritional signal, the stronger the viability (brightness) of the spores (Credit: Süel Lab/Kaito Kikuchi & Leticia Galera).

But as the number of trophic pulses increases, Bacillus subtilis begins to rejuvenate, as if they can record the number of trophic pulses, and as the number increases they know at some point that it's
time to wake up.

So the authors analyzed what was happening
inside the bacteria with each pulse of nutrition.
They found that the bacteria's energy stored in the form of potassium ions plays a role, and each stimulation causes the potassium ions to be released from the inner membrane, and when enough is released, the spores change their state and come back to life
.

Each time a nutritional signal is received, potassium ions are partially released (Credit: Lombardino & Burton, Science, 2022).

The authors note that this is a typical signal accumulation processing strategy, "which suggests that physiologically inactivated spores are actually also performing a decision-making selection mechanism
.
" Professor Süel says this strategy is not new because neurons in our brains process information
in a similar way.
Some short-lived information inputs accumulate, and when the threshold is reached, neurons are activated and transmit information to other neurons to communicate
.
It's just that in bacteria, this process is used to awaken the
spores.

This survival strategy also makes people think about possible forms of life on alien surfaces, and whether some life under extreme conditions is also waiting for an opportunity to recover?

Of course, the first thing the team needs to do is to confirm that this strategy will be used in a wider range of life, such as whether some fungi that enter a spore-like state may have done the same thing, or whether potassium concentration levels can determine the length of spore retention, which are questions
that the authors are interested in answering.