Diversity of CRISPR-Cas type II-A systems in Streptococcus anginosus

is a commensal Streptococcal species that is often associated with invasive bacterial infections. However, little is known about its molecular genetic background. Many Streptococcal species, including , harbor clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems. A CRISPR-Cas type II-A system as well as a type II-C system have been reported for this species. To characterize the CRISPR-Cas type II systems of in more detail, we conducted a phylogenetic analysis of Cas9 sequences from CRISPR-Cas type II systems with a special focus on streptococci and . In addition, a phylogenetic analysis of strains based on housekeeping genes included in MLST analysis, was performed. All analyzed Cas9 sequences of clustered with the Cas9 sequences of CRISPR type II-A systems, including the Cas9 sequences of strains reported to harbor a type II-C system. The Cas9 genes of the CRISPR-Cas type II-C systems of other bacterial species separated into a different cluster. Moreover, analyzing the CRISPR loci found in , two distinct genes could be detected, a short form showing high similarity to the canonical form of the gene present in . The second CRISPR type II locus of contained a longer variant of with close similarities to a gene that has previously been described in Since CRISPR-Cas type II-C systems do not contain a gene, the strains reported to have a CRISPR-Cas type II-C system appear to carry a variation of CRISPR-Cas type II-A harboring a long variant of .