CRISPR regions of S. mutans UA159 and NN2025. CRISPR-1 region (Region 19) in NN2025 is a newly acquired region (a), and CRISPR-2 region (Region 20) is conserved between NN2025 and UA159 (b). The ORF colors indicate the BLAST classification as shown in Figure 1. The BLASTP analysis was carried out across a non-redundant protein database in the GenBank. HP; hypothetical protein. Blue lines indicate the palindromic repeat and spacer sequences. Pink areas indicate the specific regions in each strain. Black dotted lines indicate orthologous genes that are located in identical relative positions or that are located in the inverted chromosomal regions. The whole gene list of this region for each strain is shown in additional file 2 and additional file 3.