Microbial CRISPR-Cas acts as a defense, but also as a gatekeeper controlling the flow of new genes into microbial genomes. In a recent Cell paper, Jiang et al. (2016) uncover the functional importance of transcription-dependent RNA targeting in type III-A CRISPR-Cas antiviral defense and provide insight into the co-evolution of virus-host symbioses.
Whitaker, R. J., & Vanderpool, C. K. (2016). CRISPR-Cas Gatekeeper: Slow on the Uptake but Gets the Job Done. Cell Host and Microbe. Cell Press. https://doi.org/10.1016/j.chom.2016.01.015