- We used M. tuberculosis H37Rv (absence of spacers 20–21 and 33–36) and M. bovis BCG (absence of spacers 3, 9, 16, and 39–43) as positive controls and distilled water as a negative control. The black squares indicated the presence of spacers and the white squares represent the absence of the spacers at positions 1 to 43 in the direct repeat locus
