nactivation, and corresponding phage sensi- tivity. I, mutant WTItts' s 2; II, mutan WT,pess• sis2ACRISPR1 in which CRISPR1 was deleted; Ill, mutant WToesan '::pR in which CRISPR1 was displaced and replaced with a unique repeat; IV, WT.2972' 5°::p5152, mutant of strain WT4,25,72' 5° in which CRISPR1 was