Alignment of CRISPR elements from the PXO99A, KACC, and MAFF genomes. Spacers are numbered from right (S0) to left, with the oldest elements on the right. Gaps (green boxes) indicate the positions of additional spacers in the genomes not shown here. Red lines indicate spacers shared in all three genomes, heavy black lines indicate spacers shared in just two species, and thin black lines indicate spacers that are similar but not identical between two species.
Salzberg et al. BMC Genomics 2008 9:204 doi:10.1186/1471-2164-9-204