Fig. 1

CRISPR locus in Mycobacterium tuberculosis. A Schematic representation of the genomic region containing the CRISPR-Cas genes in the reference strain H37Rv. The CRISPR region comprises 4392 bp including the IS6110 copy inserted. Cas proteins are encoded upstream regarding the transcription direction on the reverse strand. B Representation of the reconstructed ancestral CRISPR locus. Direct repeats (DR), represented in dark blue, are interspersed with the spacer sequences, each having a unique nucleotide sequence. Although the DR sequence is highly conserved, three of them harbor rare mutations indicated by asterisks. Around the IS6110 insertion, the DR are truncated, still allowing the fixation of standard spoligotyping probes pointing to the adjacent spacer. Of note, the duplication of DVR35 is not in tandem and lies next to DVR41