CRISPR

CRISPR stands for Clustered Regularly Intespaced Short Palindromic Repeats and it’s a family of DNA sequences in bacteria discovered by the Spanish researcher Francisco Mójica, who proposed them as part of the bacterial immune system against bacteriophages.

These sequences are normally linked to CRISPR-associated (cas) genes, which encode different Cas proteins with a variety of nucleic acid manipulation functions (nucleases, helicases, polymerases) to ensure the success of this mechanism of defense. Thus, when a virus infects a bacteria, the viral DNA is intercepted by Cas proteins and: a) "record that virus identity" by integrating part of the viral sequence in the bacterial genome; or b) inactivate the viral DNA if the bacteria is already immunized from a previous infection.

This way, bacteria can store information about viruses that it is used to prevent future infections.