Prophage targeting by CRISPR spacers.

<p>The heat map displays <i>Bifidobacterium</i> CRISPR spacers that target prophage sequences harbored in bifidobacterial genomes. The horizontal axis lists hosts that contain prophages that are targeted by CRISPR spacers. The vertical axis lists strains containing CRISPR spacers that target a bifibacterial prophage sequence. The color intensity represents the number of cross-targeting events with red squares being high density (up to 10 targeting events), and white squares being single targeting events. The darker pink squares correlate with higher cross-targeting events and lighter pink squares correlate with fewer events. Blue squares represent that absence of CRISPR targeting. Hits shown in grey indicate self-targeting spacers that target prophage sequences in that particular chromosome meaning both the spacer and the prophage target are in the same chromosome. The darker grey indicates four distinct spacers that target prophage sequences, while the lighter grey indicates a single self-targeting spacer.