Experimental Definition of a Clustered Regularly Interspaced Short Palindromic Duplicon in Escherichia coli

We analyzed sequences of newly inserted repeats in an Escherichia coli CRISPR (clustered regularly interspaced short palindromic repeats) array in vivo and showed that a base previously thought to belong to the repeat is actually derived from a protospacer. Based on further experimental results, we propose to use the term “duplicon” for a repeated sequence in a CRISPR array that serves as a template for a new duplicon. Our findings suggest the possibility of redrawing the borders between repeats, spacers, and protospacer adjacent motifs.