Extended Data Table 1b. Identity of acquired spacers in E. coli BL21-AI cells.

Following overnight growth with or without induction of Cas1+2, gel-separated expanded arrays were amplified and sequenced, to study the identity of newly acquired spacers in high resolution.

Sample	rep	# new spacers sequenced	# spacers from chromosome	# spacers from plasmid	% spacers from plasmid	% spacers from genome
BL21-AI, no ara	1	2,594,637	48,300	2,546,337	98.14%	1.86%
BL21-AI, no ara	2	2,056,397	35,911	2,020,486	98.25%	1.75%
BL21-AI, 0.2% ara	1	647,929	151,181	496,748	76.67%	23.33%
BL21-AI, 0.2% ara	2	851,824	190,791	661,033	77.60%	22.40%
BL21-AI pheA::TerB	1	2,937,147	46,015	2,891,132	98.43%	1.57%
BL21-AI pheA::TerB	2	3,400,210	44,748	3,355,462	98.68%	1.32%