Here is how dormant bacteria figure out the right time to become active again

They can even help us know more about aliens.
Rupendra Brahambhatt
3d illustration of a macro shot of growing mildew.
3d illustration of a macro shot of growing mildew.

Christoph Burgstedt/iStock 

Do you know bacteria have been living on Earth for the last 3.5 billion years? One of the factors that makes them such a long-lasting species is their ability to turn into dormant spores (metabolically inactive dry cells with a protective protein coating) under unfavorable environmental conditions. In the form of spores, bacteria can stay dormant and survive for even thousands of years.

However, for a long time, it has been unknown how bacteria spores know when to resume normal functioning when they are in a dormant state. Looks like now a team of researchers at the University of California San Diego (UCSD) has found the answer to this question. In their latest study, the researchers point out that dormant spores use an interesting process called “integrate and fire” to monitor their surroundings, which is very similar to the way neurons communicate with each other.

Understanding the “integrate and fire” mechanism in spores

Here is how dormant bacteria figure out the right time to become active again
Several dormant spores with their electrochemical potential color-coded.

The scientists at UCSD examined dormant Bacillus subtilis bacteria and created a mathematical model to demonstrate their findings. The model suggests that the dormant bacteria spores utilize electrochemical energy stored in their bodies in the form of potassium ions to analyze the external conditions. Without being metabolically active, the spores release stored potassium ions to detect different environmental stimuli.

There is a threshold value of stored potassium ions for dormant bacteria. When the sum total of all potassium ions released over time in response to various external stimuli crosses the threshold value, the spores become active. One of the authors and biology professor at UCSD, Gurol Suel, told IE, “The threshold is defined as a value below which the spores do not trigger a return to life. When the threshold is reached, spores exit their dormant state.”

He further added, “Mechanistically, the threshold in spores corresponds to potassium content. When spores lose sufficient potassium, they trigger a return to life.” This whole process that enables dormant spores to study their environment via the flux of their stored potassium ions before becoming active is referred to as the integrate and fire mechanism.

The researchers believe that their model is similar to the integrate and fire neuron model, a popular approach for studying the function and behavior of neurons in a neural network. Similar to how a neuron releases an action potential when its membrane potential reaches the threshold value, dormant spores also trigger activity as soon as their potassium ion flux arrives at the threshold.

However, a key difference between neurons and dormant spores is that while the former is super-active and requires a lot of energy to fire the action potential, the latter performs the same task while being in a physiologically dead state.

Dormant bacteria could help us better understand aliens

According to the researchers, it is very important to study dormant bacteria because spore formation is actually a survival technique that allows some of these microorganisms to even stay alive for thousands of years. This makes it difficult for us to eliminate harmful bacteria that contaminate the environment and spread diseases. For example, Bacillus anthrax, a bacteria that causes the deadly anthrax disease in farm animals, can survive for decades as dormant spores in the soil.

Since bacteria in their dormant state are known to withstand extreme environmental conditions (and even antibiotics). It is believed that the spores can also provide us with valuable insights about possible dormant life forms on other planets. “Scientists are actively looking for life on Mars, and it is likely that any life form to be found will be in a dormant state. Therefore, a better understanding of life in extreme dormant states on our planet may be informative to think about dormant life forms on other planets and moons,” said professor Suel.

The researchers are fascinated by the surprising capabilities of bacteria and their ability to perform complex behaviors, such as counting and summing signals over time. Therefore, they are looking for more ways to learn further about bacterial spores.

The study is published in the journal Science.

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