Extended Data Table 2a. Adaptation experiment with dnaC2 temperature sensitive cells.

E. coli K12 cells were transformed with a pBAD-Cas1+2 vector, in which the Cas1+2 operon is directly controlled by an arabinose-inducible promoter. Following overnight induction by 0.2% L-arabinose and 0.1mM IPTG, the CRISPR array was amplified and sequenced.

Sample	rep	# of reads spanning the CRISPR array	# of reads supporting unmodified parental array	# of reads supporting acquisition of a new spacer	% expanded arrays
K-12 ΔcasC 30°C	1	98,884	96,299	2,585	2.61%
K-12 ΔcasC 30°C	2	117,522	115,030	2,492	2.12%
K-12 ΔcasC, dnaC2 30°C	1	152,827	149,644	3,183	2.08%
K-12 ΔcasC, dnaC2 30°C	2	100,125	98,053	2,072	2.07%
K-12 ΔcasC, 39°C	1	87,036	83,688	3,348	3.85%
K-12 ΔcasC, 39°C	2	86,580	82,474	4,106	4.74%
K-12 ΔcasC, dnaC2 39°C	1	66,618	66,618	0	0.00%
K-12 ΔcasC, dnaC2 39°C	2	60,325	60,321	4	0.01%