Tel Aviv University Researchers Find Way Virus and Bacteria Communicate

A new study from Tel Aviv University TAU has found that viruses called bacteriophages (or phages) are so advanced that they actually make decisions based on whether the time has come to exit the dormant state and attack their bacterial host. Accoording to TAU, They do so based on weighing all options before finally making an informed decision. In this way, viruses act just like humans do with Game Theory.

Game Theory, explains Investopedia, is a theoretical framework for conceiving social situations among competing players. In some respects, game theory is the science of strategy, or at least the optimal decision-making of independent and competing actors in a strategic setting.

This is the sort of thing used by businesses when deciding on a course of action for sales and marketing, whether to release a new product and so forth. The military also uses Game Theory when trying to understand how an opponent might react to a given move that it plans on making. And diplomats the world over use it to try and understand what they can expect from other countries in response to overtures, or hostile actions made by their own nation.

But virus? Does this mean that we will now be able to use rational study to see what will come next from the Coronavirus? Does it mean that viruses need to be dealt with like people? No, of course not. But it could mean that someday in the near future they will be able to shop any stop any kind of virus and preclude any possibility of a pandemic. It could even mean the possibility of a preemptive vaccination for all people against any and all viruses.

The TAU study was led by Prof. Avigdor Eldar of the Shmunis School of Biomedicine and Cancer Research at Tel Aviv University, together with his students and partners from the Weizmann Institute of Science. The paper was published in December 2021 in the journal Nature Microbiology.

Phages are viruses that attack bacteria. Many phages can exist in one of two states: active (lysis), in which the phages attack and destroy bacteria, or dormant, in which they remain passive within the bacteria, replicating themselves but doing no damage (lysogeny). Phages of this type must decide whether to be active or dormant every time they infect a new host. If they decide to be dormant for a time, they must also decide when to ‘wake up’ and attack. As in all dilemmas, it’s important to base the decision upon solid, reliable information.

According to the researchers, it has been assumed for some time that a phage bases its decision to exit the dormant state on information regarding condition of its bacterial host: when the host shows signs of substantial DNA damage (death throes, so to speak), it is in the phage’s interest to leave it and try to infect other bacteria.

The new study discovered an additional mechanism of communication between bacteria and phages: apparently, some phage families have developed a more complex decision-making strategy, a kind of ‘phage game theory’, in which the phage receives information not only from its own host but also from neighboring bacteria.

Prof. Eldar explains, “When a phage is dormant within a bacterial cell, it forces its host to constantly produce small communication molecules called arbitrium, to which the phage listens via a special receptor. Thus, the presence of high levels of these molecules indicates that neighboring bacteria also contain phages. When this happens, even if its own host exhibits DNA damage, the phage refrains from becoming active. Since every bacterium can only host one dormant phage, the phage makes an informed decision: it’s better to let the host try to repair itself than to ‘betray’ it, since all neighboring bacteria are already taken.”

Prof. Eldar and his team used a range of genetic and biomolecular methods to track the biochemical communication signals passing between the bacteria and phages. In a former study they used a fluorescent marker to show that communication methods used by phages, as well as a large family of similar communication systems (know generally as ‘quorum sensing’) are used only to get signals from close neighbors. “Essentially, the bacteria have developed two separate communication systems – one for long-range communication, and the other for short distances only, used to sense the state of their immediate neighbors,” says Prof. Eldar. “In the phage’s case, it controls communication, and is only interested to know whether its close neighbors, which it might easily infect, are already occupied.”