Figure 2.

Killing, genome editing or modulation of gene expression by CRISPR-Cas systems. CRISPR-Cas systems can be delivered to target bacteria either in vitro or in vivo through transformation, transduction or conjugation. Cas nucleases induce DNA breaks that can either lead to DNA degradation and cell death, or if the break is repaired to the introduction of mutations. Catalytically dead Cas proteins such as dCas9 can be used to silence genes by blocking the RNA polymerase (RNAP). Dead Cas proteins can also be fused to various protein domains such as activators to induce the expression of genes, or to domains able to modify DNA bases.