BacteRiophage EXclusion (BREX): A novel anti-phage mechanism in the arsenal of bacterial defense system.

The arm race between bacteria and phages leads to the development of many phage resistance mechanisms. Bacteria are perpetually changing their strategy to avert phage infection and killing. Recently, a study published that shed light on a novel bacterial defense system called bacteriophage exclusion (BREX). BREX system is a six-gene cassette in Bacillus cereus which provides complete phage resistance to a broad range of phages, including lytic and temperate ones. It is a novel defense strategy which involves DNA methylation of the host cell and block phage DNA replication.