From 1987 and during the following 20 years, a few research teams exploring bacteria and archea genome sequences uncover the prokaryotic adaptative immune system made of the CRISPR sequence and associated cas genes. First believed to be similar to the eukaryote RNA interference system, CRISPR-Cas turned out to be unique and of an amazing genetic complexity. The comparative studies of CRISPR arrays and of cas, and later of microbiotes metagenomes allowed to propose an evolution scenario for these systems. The results demonstrate the importance of a naturalistic approach, without a priori, for the understanding of living organisms.
© Société de Biologie, 2018.