A widespread novel ncRNA-dependent family of anti-phage defense systems

In order to defend against phages bacteria can utilize different mechanisms. The use of non-coding RNA in bacterial anti-phage defense is known from two examples: CRISPR-Cas systems, where the crRNA guides the CRISPR nuclease to the invading nucleic acid, and some toxin-antitoxin systems which use ncRNAs as an antitoxin. In our recent systematic search for novel anti-phage defense systems, we have identified a new widespread family of defense systems that is dependent on a non-coding RNA for defense against phages. We demonstrate through mutational analyses that specific elements in the sequence and in the structure of the ncRNA are essential for defense. This discovery expands our knowledge on the different mechanisms employed by bacteria to defend against phages.