Salmonella CRISPR loci.Salmonella have two CRISPR loci, CRISPR1 and CRISPR2 comprised of direct repeats of 29 nucleotides (black diamonds) separated by spacers (empty rectangles). There is an A-T rich leader sequence upstream of each locus (shaded rectangle) and the CRISPR-associated genes (cas) are upstream of the CRISPR1 locus (grey boxed arrow). Primers used for amplification are shown in blue and red for CRISPR1 and CRISPR2, respectively.
Shariat et al. BMC Microbiology 2013 13:254 doi:10.1186/1471-2180-13-254