When extreme environments come and are no longer suitable for survival and reproduction, bacteria will transform into spores. This transformation allows bacteria to gain super resistance. The spores can tolerate extreme dryness, temperature and pressure. For example, some pathogenic bacteria can remain in the soil for several years after being converted into spores, and will wake up again when the environment is suitable.
But scientists have always believed that spores are in a very vague state of life. Strictly speaking, spores do not perform deep sleep like hibernating animals. They are no different from death from physiological perspectives, because spores do not have any metabolic activity .
Image source: 123RF
But it is surprising that such a dead spore can know when to wake up. As long as the time is right, bacteria can resurrect and reproduce and expand the troops. This process has also fascinated many microbiologists.
Recently, a new study by "Science " discovered for the first time the small mystery of spores "resurrected from the dead". Although they are not metabolized, they can be adjusted by means of charged particles stored inside, and tell themselves the external nutritional level according to the slight changes in the particles, thus deciding whether to wake up.
"This study changed our view on bacterial spores, which we used to think were extremely inert objects," said Professor Gürol Süel, a molecular biologist at at the University of California, San Diego. The spores still retain the ability to process information, especially uses electrochemical potential energy to "calculate" the nutritional changes around it, a process that does not require metabolic participation in at all.
New study selected thousands of spore states of Bacillus subtilis for real-time tracking. These bacteria have extremely strong viability and can even survive stress tests in space for a long time.
studies will give very short nutrient pulses in their environment, and the nutritional signal provided by a single time is not enough to directly resuscitate the spores. According to the author's follow-up observation, the previous few nutritional pulses did seem to have happened, and the spores were still lifeless.
▲The stronger the nutritional signal, the stronger the spores are (higher the brightness) (Image source: Süel Lab/Kaito Kikuchi & Leticia Galera)
But as the number of nutrient pulses increases, Bacillus subtilis begins to regain vitality. They seem to be able to record the number of nutrient pulses. As the numbers increase, they know at some point that it is time to wake up.
So the author analyzed what happened inside the bacteria every time the nutrient pulse was. They found that the energy stored by the bacteria in the form of potassium ion will play a role in . Each stimulus can release the potassium ions from the inner membrane. When it is released enough, the spores will change its state and resurrect it.
▲Every time a nutrient signal is received, the potassium ions will be partially released (Image source: Lombardino & Burton, Science, 2022)
The author points out that this is a typical signal accumulation processing strategy, "This shows that physiologically inactivated spores are actually implementing a decision-making selection mechanism." Professor Süel said that this strategy is not unfamiliar, because the neurons in our brain process information in a similar way. Some short-term information inputs will accumulate continuously. When the threshold is reached, the neurons will be activated and transmit information to other neurons for communication. is just in bacteria, and this process is used to awaken spores.
This survival strategy also makes people think about the possible forms of life in aliens. Are some lives under extreme conditions waiting for an opportunity to recover?
Of course, the first thing the research 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 taken the same approach, or whether the concentration level of potassium ions can determine the length of spores. These are questions that the author is very interested in and wants to answer.
Reference:
[1] Unexpected Activity in 'Dead' Bacteria Detected by Scientists. Retrieved October 11, 2022 from https://www.sciencealert.com/unexpected-activity-in-dead-bacteria-detected-by-scientists,
[2] Electrochemical potential enables dormant spores to integrate environmental signals. Science (2022). DOI: https://doi.org/10.1126/science.abl7484
