CRISPR spacer acquisition under priming. Legionella pneumophila subsp. pneumophila strain:Toronto-2005

CRISPR-Cas is a bacterial adaptive immune system that uses short, invader-derived sequences termed spacers to target invasive nucleic acids. Upon recognition of invaders previously encountered, the system can stimulate secondary spacer acquisitions, a process called priming. Here, we take advantage of a native type I-C CRISPR-Cas system in Legionella pneumophila that shows relatively permissive interference but robust primed adaptation even with bona fide targets. We used Illumina sequencing approaches to analyze acquired spacers under priming, and performed a plasmid-removal based screen to examine functional PAMs for interference.