LAUSR

CRISPR-Cas systems provide RNA-guided adaptive immunity to the majority of archaea and many bacteria. They are able to capture pieces of invading genetic elements in the form of novel spacers in an array of repeats. These elements can then be used as a memory to destroy incoming DNA through the action of RNA-guided nucleases. This chapter describes general procedures to determine the ability of CRISPR-Cas systems to capture novel sequences and to use them to block phages and horizontal gene transfer. All protocols are performed in Staphylococcus aureus using Type II-A CRISPR-Cas systems. Nonetheless, the protocols provided can be adapted to work with other bacteria and other types of CRISPR-Cas systems.