Game Theory may be useful in combatting viruses- TAU study

A 'phage game theory' exists, in which the phage receives information not only from its own host but also from neighboring bacteria.

 Bacteria which contain a "dormant" parasitic element (blue) are awakening and getting yellow in the presence of bacteria which do not contain the element (red). (photo credit: COURTESY/TEL AVIV UNIVERSITY)
Bacteria which contain a "dormant" parasitic element (blue) are awakening and getting yellow in the presence of bacteria which do not contain the element (red).
(photo credit: COURTESY/TEL AVIV UNIVERSITY)

A game-theory approach may offer new insights into both the spread and disruption of viruses, called bacteriophages (or phages),  a team of researchers from Tel Aviv University has concluded.

The peer-reviewed research, described last month in the journal Nature Microbiology, suggests that the viruses weigh all options and finally make an informed decision about whether the time has come to exit the dormant state and attack their bacterial host.

According to the scientists, it has been accepted based on previous research that a phage decides to exit the dormant state based on information regarding the condition of its bacterial host. When the host shows signs of substantial DNA damage, it is in the phage's interest to leave it and try to infect other bacteria.

There is a more complex decision-making strategy, though, according to this study. A 'phage game theory' exists, in which the phage receives information not only from its own host but also from neighboring bacteria.

Prof. Avigdor Eldar, who led the study, used a range of genetic and biomolecular methods to track the biochemical communication signals passing between the bacteria and phages. "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," he said.

When this happens, even if its own host exhibits DNA damage, the phage refrains from becoming active, Eldar said. "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."

 Tel Aviv University Campus (credit: COURTESY TEL AVIV UNIVERSITY) Tel Aviv University Campus (credit: COURTESY TEL AVIV UNIVERSITY)

Eldar noted that several years ago, the Weizmann Institute identified this communication for the first time. “Such systems had been known to exist between other molecular parasites hosted by bacteria called plasmids,” he said. “Our new discovery is the fact that phages use communication even in their dormant state.

"We have identified components critical for understanding how phages combine information about their host's condition with information about their neighbors," Eldar said. "This is one more important step on the way to deciphering the communication and 'behavioral economics' of viruses.

"Phages have an excellent ability to process information and make the right decision to ensure optimal survival. It will be interesting to see whether viruses residing in more complex organisms but facing similar decisions have also developed comparable systems of communication."