Cas9 determines the PAM sequence of acquired spacersa, c, Genetic composition of the CRISPR-Cas loci tested for spacer during phage infection (a), or in the absence of infection, with the experimental set up shown in Fig. S4 (c). b, d, Sequence logos obtained after the alignment of the 3' flanking sequences of the protospacers matched by the newly acquired spacers in panels a and c, respectively. Numbers indicate the positions of the flanking nucleotides downstream from the spacer. n; number of sequences used in each alignment.
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