CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Plasmid targeted by CRISPR locus P1 transform wild-type cells very poorly (PubMed:22767603). This protein processes pre-crRNA into individual crRNA units, in vivo at least Cas5 and Cas7 are also required for optimal crRNA processing and/or stability (PubMed:24459147). Component of the Cascade-like complex (Cascade I-B), composed of Cas5, Cas6, Cas7 and crRNA. Expressed in exponential and stationary phases. Loss of the 8 Cas genes in this locus (cas1, cas2, cas3, cas4, cas5, cas6, cas7 and cas8b) leads to loss of CRISPR interference against plasmid targeted by this CRISPR locus, i.e. plasmid is not destroyed by CRISPR (PubMed:22767603). Upon disruption of only this gene, no visible phenotype when grown under differing temperature and salt regimes. Does not produce mature length crRNA. Can be complemented by endogenous Cas6, but not by Cas6 from halophilic archaea H.lacusprofundi, or non-halophilic archaea M. maripaludis or M. mazei. Loss of CRISPR interference against plasmid targeted by this CRISPR locus, i.e. plasmid is not destroyed by CRISPR action (PubMed:24459147). There are 3 CRISPR RNA loci in this organism and a single cas gene locus. A CRISPR-Cas type I-B system. Belongs to the CRISPR-associated protein Cas6/Cse3/CasE family.