Specialized weaponry: how a type III-A CRISPR-cas system excels at combating phages

CRISPR-Cas-mediated defense against phage invaders usually requires recognition of short sequences, termed protospacer-adjacent motifs (PAMs), in phage DNA. In this issue of Cell Host & Microbe, Pyenson et al. (2017) show that the lack of a PAM requirement in some CRISPR-Cas systems prevents interference evasion and facilitates phage extinction