The study opens promising avenues for novel approaches to combat bacterial pathogens.

The findings, published in the peer-reviewed Nature Microbiology journal, present a sophisticated mechanism in which viruses co-opt bacterial defense systems to regulate their behavior.

Researchers at Tel Aviv University, led by Ph.D. student Polina Guler, under the guidance of Professor Avigdor Eldar, focused on bacteriophages, viruses that infect bacteria. Contrary to their predatory name, bacteriophages often maintain a symbiotic relationship with their bacterial hosts, residing in a dormant state within the host genome.

However, they possess the ability to turn violent, swiftly replicating and destroying their host under certain conditions.

The decision-making process of bacteriophages relies on two key factors: the health status of the host bacteria and external signals indicating the presence of other phages. If a bacteriophage senses a compromised host but perceives the availability of unoccupied hosts nearby, it opts for aggression, swiftly replicating and killing its current host to seek out new targets. Conversely, if signals suggest a crowded phage environment, it remains dormant, awaiting more favorable conditions.

Remarkably, the study described how bacteriophages manipulate a bacterial defense system to execute this decision.

“The phage actually uses a system that the bacteria developed to kill phages,” Guler explained. In the absence of signals from other phages, indicating potential hosts, the bacteriophage disables the bacterial defense system, enabling it to replicate unchecked and kill the host. Conversely, in the presence of such signals, it utilizes the defense system to maintain dormancy, ensuring its survival within the host genome.

While bacterial defense systems against virulent viruses have been extensively studied, mechanisms pertaining to viruses with dormant modes have remained largely unexplored. Understanding these interactions is crucial, particularly considering the implications for human health.

“Some bacteria, such as those causing cholera, become more virulent if they carry dormant phages – the main toxins harming us are encoded by the phage genome,” Eldar said.

He added that bacteriophages hold potential as alternatives to antibiotics against pathogenic bacteria. Additionally, insights gained from phage research could enhance understanding of human-infecting viruses, many of which exhibit dormancy and virulence cycles.

By deciphering the mechanisms governing virus behavior, scientists move closer to harnessing these entities for therapeutic purposes and gaining deeper insights into viral infections and how to fight them.

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