Fig. 4.
Engineered CRISPRs confer resistance to λ in the presence of Cascade and Cas3. (A) Effect of the presence of different sets of cas genes on the sensitivity of E. coli to phage λvir. Cells were equipped with one of two engineered CRISPRs containing four anti-λ spacers each (fig. S3). The C1–4 CRISPR produces crRNA complementary to the coding strand and mRNA of λvir, and the T1–4 CRISPR targets only the template strand. The sensitivity of each strain to phage λvir is represented as a histogram of the efficiency of plaquing, which is the plaque count ratio of the anti-λ CRISPR to that of the nontargeting control CRISPR. (B) Effect of single anti-λ spacers (fig. S3) on the sensitivity of E. coli to λvir. Error bars indicate 1 SD.