Table 3.

Spacer sequences repeated either within a cluster or between different clusters of the same organism.

Organism/ plasmid	Repeated once in a cluster	Repeated more than once in a cluster	Present in different clusters	Total no. of repeated spacers
H. butylicus	2			4
S. solfataricus	1		3	8
S. tokodaii	2	1	5	17
S. acidocaldarius	2	1		9
P. furiosus	1		3	8
P. torridus	10			20
A. fulgidus			1	2
M. jannaschii	2	2		14
M. thermautotrophicus	18			36
M. barkeri	1			2
M. mazei	2			4
H. marismortui pNG300	1			2
H. marismortui pNG400	2			4