Bacteriophage exclusion, a new defense system

The ability to withstand viral predation is critical for survival of most microbes. Accordingly, a plethora of phage resistance systems has been identified in bacterial genomes (Labrie etal, ), including restriction-modification systems (R-M) (Tock & Dryden, ), abortive infection (Abi) (Chopin etal, ), Argonaute-based interference (Swarts etal, ), as well as clustered regularly interspaced short palindromic repeats (CRISPR) and associated protein (Cas) adaptive immune system (CRISPR-Cas) (Barrangou & Marraffini, ; Van der Oost etal, ). Predictably, the dark matter of bacterial genomes contains a wealth of genetic gold. A study published in this issue of The EMBO Journal by Goldfarb etal () unveils bacteriophage exclusion (BREX) as a novel, widespread bacteriophage resistance system that provides innate immunity against virulent and temperate phage in bacteria.