CRISPR is so popular even viruses may use it

The tool for editing genes started out as a defense against invaders. It turns out the intended targets stole the technology for their own use. A new study shows that thousands of the bacteriophages contain the genes of the CRISPR system, suggesting that they may be used to attack rivals. The finding is a testament to the power of the weapon.

Mazhar Adli of the Feinberg School of Medicine was not connected to the research.

phages can't reproduce on their own bacteria are able to fight back Sequences of previously encountered phages are included in the repetitive stretches of DNA. If these same phages attack a bacterium again, they use this repetitive DNA to cut the phage's genome with a pair of genetic scissors. Over the past decade, scientists have been working to turn the immune defense into a technique that can be used to fight diseases such as cancer.

There are a number of phages that have turned up with characteristic DNA. According to structural biologists at the University of California, Berkeley, who shared the 2020 Nobel Prize in Chemistry for showing how to tailor the CRISPR system to target particular sequence, these finds were just curiosities. We wondered if these systems were more common.

They went looking for more examples of CRISPR in the phage world. They probed the genetic material from a variety of environments, including the human mouth and soil. The scientists found more than 6000 types of phages that contain the CRISPR system. They looked at the genomes that had been uploaded to online databases and found more instances of the viruses. The researchers didn't expect a broad distribution of an anti-phage system in phages.

Why would a system evolve to stop them? It is most likely that the reason is to beat the other team. She says that multiple viruses can attack a bacterium at the same time. The cells are vulnerable to rogue DNA strands that force them to copy something. phages can have the replication machinery all to themselves if they destroy their rivals.

She says that the phages probably stole the CRISPR system sequence from their victims. The viruses have made their own modifications to the systems. It is possible that some phages have lost their ability to generate certain molecules that can killbacteria in order to preserve their host's production of more phages.

New biotechnology may be inspired by the phages. Most CRISPR-based approaches now rely on theCas9 to cut DNA. It can't fit into some of the viruses used to modify cells A number of phages have a version that is half the size of the original. Researchers would need to overcome several hurdles in order to be able to modify plant genomes with this smalleridase.

Microbiologist Joseph Bondy-Denomy of UC San Francisco says that the synergy between the two scientists was amazing. He wants to know if the phages put their systems to use when they invadebacteria. According to Bondy-Denomy, there are many more phages that are waiting to be found. He says there is more to come.