A bacteriophage nucleus like compartment shields DNA from CRISPR nucleases.

Order of authorship in the original publication: Mendoza, Nieweglowska, Govindarajan. The authors showed that the large phage that specifically infects a Pseudomonas bacterium segregates its DNA, which the phage CRISPR would attack and destroy, by building a proteinaceous compartment or wall around its DNA. This protein barrier makes its DNA inaccessible to the CRISPR nuclease attack and destruction. This could be called the operation of natural selection at the molecular level.

(Thanks to Juan Weiss for this reference and its interpretation.)