Figure 4. Multi-spacer colonies have impaired growth.

(A) Enumeration of colony forming units (CFU) obtained after infection of staphylococci carrying pCRISPR or pCRISPR(Δcas2) plasmids (clear or dashed pattern bars), containing spacer C or F (red or blue bars, respectively), with ϕNM4γ4 or ϕNM4γ4 also containing spacer F escaper phage. Mean ± StDev values of three independent experiments (black dots) are shown. (B) Images of bacteriophage-resistant colonies 1 or 2 days after infection with ϕNM4γ4 phage, and PCR analysis of the spacer content in their pCRISPR plasmid. (Barrangou et al., 2007), one spacer control. (C) Same as (B) but with colonies that experienced growth over time; their letter name colored according to the spacer content: red, mono-spacer; blue, multi-spacer.