Until now, however, it was not known how spacers are stolen from the foreign invader's genome and transferred into the CRISPR loci of the host. Working with the bacteria E. coli and using high-through¬put sequencing of spacers inserted in vitro, Doudna, Nuñez and their colleagues found that the memorizing proteins - Cas1 and Cas2 - recognize repeating sequences in CRISPR loci and target these sites for the spacer insertion process.