The most widespread systems were known to defend the host by degradation of nucleic acids, such as CRISPR-Cas (with CRISPR-Cas I-E in 68 strains) and restriction modification systems (RM type I in 45 strains, RM type II in 41 strains, RM type IIG in 18 strains, RM type III in 3 strains, and RM type IV in 45 strains), or by abortive infection, such as CBASS (CBASS type I in 14 strains, CBASS type II in 33 strains) and probably AVAST (AVAST type II in 33 strains and AVAST type I in 1 strain) (Fig. 2). Here, CA1 is linked to infection.