Consistent with Acr-phages only being able to successfully overcome CRISPR resistance at high phage densities, we observed at 2 days post-infection (dpi) an invasion of bacteria with surface-based resistance under high Acr-phage-density treatments, which was accompanied by a reduction in relative fitness of CRISPR-resistant bacteria (Figure S3; F1,17 = 48.9, p < 0001). Here, ACR is linked to infection.