Table 1. Taxonomic distribution of CRISPR-Cas types and sub-types in prokaryotes expressed in number and percentage of the genomes harboring the systems.

Typing	Type I							Type II			Type III			Type U
Bacteria	769 (31%)							177 (7%)			222 (9%)			7
Archaea	113 (71%)							0			60 (38%)			0
Subtyping	I-A	I-B	I-C	I-D	I-E	I-F	I-U	II-A	II-B	II-U	III-A	III-B	III-U	U
Bacteria	16 (<1%)	173 (7%)	196 (8%)	31 (1%)	282 (11%)	111 (5%)	47 (2%)	81 (3%)	5 (<1%)	93 (4%)	123 (5%)	112 (5%)	3 (<1%)	7 (<1%)
Archaea	55 (35%)	48 (30%)	2 (<1%)	16 (10%)	5 (3%)	0	2 (1%)	0	0	0	28 (18%)	40 (25%)	0	0