title: The highly dynamic CRISPR1 system of Streptococcus agalactiae controls the diversity of its mobilome.
abstract: Clustered regularly interspaced short palindromic repeats (CRISPR) confer immunity against mobile genetic elements (MGEs) in prokaryotes. Streptococcus agalactiae, a leading cause of neonatal infections contains in its genome two CRISPR/Cas systems. We show that type 1-C CRISPR2 is present in few strains but type 2-A CRISPR1 is ubiquitous. Comparative sequence analysis of the CRISPR1 spacer content of 351 S. agalactiae strains revealed that it is extremely diverse due to the acquisition of new spacers, spacer duplications and spacer deletions that witness the dynamics of this system. The spacer content profile mirrors the S. agalactiae population structure. Transfer of a conjugative transposon targeted by CRISPR1 selected for spacer rearrangements, suggesting that deletions and duplications pre-exist in the population. The comparison of protospacers located within MGE or the core genome and protospacer-associated motif-shuffling demonstrated that the GG motif is sufficient to discriminate self and non-self and for spacer selection and integration. Strikingly more than 40% of the 949 different CRISPR1 spacers identified target MGEs found in S. agalactiae genomes. We thus propose that the S. agalactiae type II-A CRISPR1/Cas system modulates the cohabitation of the species with its mobilome, as such contributing to the diversity of MGEs in the population.
authors: Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram Positif, Paris, France.
authors: Maria-José
authors: MJ
authors: Lopez-Sanchez
authors: Elisabeth
authors: E
authors: Sauvage
authors: Violette
authors: V
authors: Da Cunha
authors: Dominique
authors: D
authors: Clermont
authors: Elisoa
authors: E
authors: Ratsima Hariniaina
authors: Bruno
authors: B
authors: Gonzalez-Zorn
authors: Claire
authors: C
authors: Poyart
authors: Isabelle
authors: I
authors: Rosinski-Chupin
authors: Philippe
authors: P
authors: Glaser
mesh_terms: D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D020071:Interspersed Repetitive Sequences; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D013292:Streptococcus agalactiae / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial