All forms of life require immune systems to stave off infection from viruses and other pathogens. In bacteria and archaea, clustered regularly interspaced short palindromic repeats (CRISPR) arrays and CRISPR-associated (Cas) proteins provide adaptive immunity against invading DNA from bacteriophages and plasmids. During infection, host cells adapt by storing short segments of foreign DNA in CRISPR arrays, providing heritable molecular memories of the infection. CRISPR-derived RNAs guide Cas complexes to bind and cleave the specific matching region of the foreign nucleic acids, thus neutralizing the infection. The unique, programmable DNA cleavage activity of CRISPR-Cas systems has been widely adapted for genome editing. In addition to providing revolutionary biotechnological tools, fundamental research into CRISPR/Cas systems has deepened our understanding of the complex molecular warfare that occurs between bacteria and their invaders. I will present recent mechanistic insights into CRISPR-Cas systems that reveal how bacteria adapt to rapidly evolving viruses.

Learning Objectives: 

1. An overview of the basic biology of CRISPR-Cas adaptive immune systems
2. The importance of specificity during CRISPR-Cas immunity
3. How guide RNA sequences can affect immunity and how these sequences are acquired in bacteria