“It has been known for a long time that prokaryotes do not have an immune system like the one in vertebrates that uses antibodies. However, it was recently discovered that they have a genetic system that kind of works like immunological memory against invading bacteriophages.
It is called clustered, regularly interspaced short palindromic repeats (CRISPR) and can be found in the genome of many prokaryotes. It works by stealing these sequences from invading viruses, sticking them in their own genomes and combining it with Cas proteins that together seek out and destroy viral sequences that match.
A version of this system, but done in reverse, is called CRISPR-Cas9 and allows scientists to use a cheap and effective biotech tool to edit genes to produce changes to an organism. In the future, this technology will likely be used routinely to modify crops to produce higher yield, eliminate harmful substances and produce useful nutrients and even treat human diseases.”