Vibrio Cholerae CRISPR-cas PAM requirements
Plasmids were constructed harboring protospacers that are perfect targets for spacers #4 and #21 of the array, but contain NNN (all possible PAM combinations) immediately upstream of the protospacer.  The plasmids were introduced into V. cholerae with or without a functional CRISPR-cas system and cells were plated on selective media.  Cells were collected and the protospacer plasmids were sequenced in a high throughput manner.  PAMs were counted using a custom python script