CRISPR-Cas: to take up DNA or not-that is the question.

Landmark experiments in the 1920s showed that capsule switching is critical for Streptococcus pneumonia survival. Further studies demonstrated that capsule "transformation" occurs via DNA uptake. In this issue of Cell Host and Microbe, Bikard et al. (2012) show that CRISPR-Cas systems inhibit DNA uptake, selecting for the outgrowth of CRISPR-defective pneumococci.