Natural Diversity of CRISPR Spacers

Hyperthermophilic archaea of the order Sulfolobales harbor some of the most complex among the studied CRISPR-Cas systems: most of the genomes contain several CRISPR arrays with different CRISPR repeats, several adaptation modules for acquisition of new spacers into CRISPR arrays and several type I and type III interference modules that degrade the DNA and/or RNA molecules of encountered mobile genetic elements (MGEs). The sequence of each CRISPR spacer and its position in the array, respectively, provide information about the encountered MGEs and the order of their interaction with the host.