It's not every day we get to see an arms race in action. Every gory detail is laid out by Paez-Espino et al in the March/April issue of mBio*. The authors use deep DNA sequencing to track CRISPR acquisition in the bacterium Streptococcus thermophilus when challenged with Streptococcus phage 2972 (a phage featured in Life in Our Phage World). 

As S. thermophilus evolved in the presence of 2972, its CRISPR loci acquired new spacers employed to recognize future invasions of 2972 phage DNA, thereb...

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