Molecular biologists from the USA have adapted the popular CRISPR/Cas13 genomic editor to work with the genome of bacteriophage viruses. This will make it possible to create new variations of viral drugs for bacterial infections, the researchers write in an article in the journal Nature Microbiology. Many bacteriophages have high potential to fight microbes, but studying and manipulating the genome of these viruses is difficult because their DNA is packaged in a kind of "protein core" that protects its strands from bacterial "antiviruses." The researchers write they adapted the CRISPR/Cas13 RNA editor to work with the genome of these bacterial pathogens. The CRISPR/Cas9 system is a kind of genetic "antivirus" that finds and destroys traces of viral DNA in the microbe's genome. A group of molecular biologists led by Joseph Bondi-Denomy, an assistant professor at the University of California, San Francisco, has adapted one version of this genomic editor, CRISPR/Cas13, to work with the genome of bacteriophage viruses. Bacteriophages are those viruses that attack microbes and pose no threat to humans. They are often seen as a possible substitute for antibiotics. So far, this is hampered by the fact that microbes quickly mutate and acquire protection against many broad-spectrum bacteriophage viruses. Bondi-Denomi and colleagues have developed an approach that will circumvent this problem by making point modifications to the DNA of these viruses. This system works indirectly - it makes changes not in the DNA of the virus itself, but in its RNA copies, which are used to produce new viral particles within infected microbes. In a similar way, scientists bypass the defense systems of bacteriophages. To do this, the scientists modified the structure of the Cas13 enzyme so that it did not destroy the entire copy of the viral genome, but removed only that part of the chain which matched the structure of one of the short RNA templates. The researchers tested the work of this system on bacteriophages FKZ, OMKO1 and PaMx41, which affect Pseudomonas bacillus. Subsequent experiments confirmed that a modified version of the Cas13 enzyme had allowed scientists to insert several foreign pieces of DNA into the genome of bacteriophages FKZ, OMKO1 and PaMx41 to make these viruses glow or produce different proteins. Such successes, the scientists believe, pave the way for the accelerated development of drugs based on genetically modified bacteriophages.