Viruses can either help or harm their hosts' immune systems

Scientists from Tel Aviv University have revealed that some viruses known as bacteriophages (ones that target bacteria) make sophisticated life-or-death decisions. These viruses can infect a bacteria’s immune system and either live peacefully within it or become a microscopic killing machine.

What makes them switch tactics? Surprisingly, the viruses tap into the very immune system their bacterial host uses to fight them off.

Relationship of virus and bacteria

Bacteriophages, or phages for short, have a surprising amount of flexibility when they encounter a new bacterium. Instead of always going on a rampage, they can integrate their own genetic code into the bacterium’s DNA.

Sometimes, this turns into a surprisingly beneficial partnership. The phage gets a cozy home, and the bacterium may even pick up some advantages from the viral genes.

But it’s not always a happy ending – phages can turn destructive in the blink of an eye.

Viruses control the immune system

Bacteria use their own immune system during phage attacks. Now, the scientists have discovered that the viruses essentially manipulate this immune system and use it to control their own fate.

It’s a bit like a burglar disabling the security system before deciding whether to fully rob the house.

“We discovered that in this process the phage actually uses a system that the bacteria developed to kill phages,” says Polina Guler, a PhD student involved in the research.

Virus harming host’s immune system

Phages aren’t just attackers; they’re also surprisingly sneaky spies. They eavesdrop on chemical signals released by other phages in the area.

If there aren’t many signals, they realize there might be greener pastures – other bacteria to infect where they won’t face competition. That’s when they pull their most devious trick.

The phage sabotages the bacterium’s defenses, essentially launching a hostile takeover that ends in the bacterium’s destruction and the virus multiplying to spread further.

Viruses helping host’s immune system

If the bacteria is “crowded” with rival phages, the virus plays nice to avoid losing its current home. In this case, instead of disabling the immune system, the virus manipulates it into triggering a dormant mode.

“The phage switches to its violent mode, and with the defense system neutralized, it is able to replicate and kill its host,” describes Guler.

Study significance

“This finding is important for several reasons… some bacteria… become more violent if they carry dormant phages inside them.” explains Professor Avigdor Eldar, who led the research team.

This discovery isn’t just about bacteria-infecting viruses. It has far-reaching implications:

Fighting disease

Some bacteria, like those that cause cholera, become much more dangerous if they’re carrying dormant phages. Understanding how phages turn these bacteria into toxins factories could lead to new disease-fighting strategies.

Alternatives to antibiotics

With antibiotic resistance on the rise, scientists are desperate for alternatives. Phages, with their ability to target specific bacteria, could be the solution we need.

Understanding viruses

Many human-infecting viruses can go dormant and reactivate later. This phage research could offer vital clues into how we might manipulate that behavior.

This discovery reveals that viruses, even the tiniest ones, might be far more strategic than we ever suspected. The line between mindless destroyer and calculating survivor is much blurrier than we once thought.

The study is published in the journal Nature Microbiology.

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