science-junkie:

Image credit: Dr Graham Beards.

The only virus with an immune system

Species: the ICP1 bacteriophage – vs. – its victim Vibrio cholerae.
Habitat: identified in south Asia, engaged in mortal battle.

The tiny virus, barely 200 nanometres long, is about to infect its favourite victim: Vibrio cholerae, the species that causes cholera. This vast bacterium has an arsenal of defences that help it get rid of viruses, but they will be no good this time.

That’s because the attacker, ICP1, has a secret weapon. It carries a set of immune system genes that one of its ancestors stole from a previous victim. Immune genes are normally a form of self-defence, but ICP1 uses them as assault weapons. With these big guns, it overpowers the bacterium’s defences.

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