In the Anti-CRISPR Jungle, Only the Weak Thrive?

If, as we all know, only the strong survive, why do bacterial viruses (phages) encode weak suppressors of a bacterial immune system? In this issue of Cell Host & Microbe, Chevallereau et al. (2019) expertly demonstrate how, in the context of competition with other phages, weakness can be a strength.

[The CRISPR-Cas system: beyond genome editing]. / Le système CRISPR-Cas - Au-delà de l'édition génomique.

CRISPR-Cas is an adaptive immune system used by many microbes to defend against nucleic acids invasion such as viral genomes. The microbial system uses its CRISPR locus to store genetic information that will generate short CRISPR RNAs. The latter with endonucleases (Cas) prevent future viral infections. Parts of this system were exploited to develop a powerful genome editing tool that was adapted for a variety of organisms. The ability of the CRISPR-Cas9 technology to effectively and precisely cut a targeted genomic DNA region has the potential to may be one day cure genetic diseases. The malleability of this editing tool also offers a wide range of possibilities from modulations of gene expression to epigenetic modifications. The natural CRISPR loci found in bacteria can be used to differentiate microbial strains or to study the interactions between bacteria and its habitat. Addressing CRISPR-Cas fundamentals in microbes and its popular use in eukaryotes, this review presents an update on a system that has revolutionized biological sciences.