[ODP-052] プロファージ上のType II メチル化酵素を介したStreptococcus pyogenesのゲノム多様化
The roles of DNA methylation caused by restriction-modification (RM) systems in bacteria including gene regulation, segregation, and mismatch repair are increasingly recognized. To assess the diversity of RM systems in Streptococcus pyogenes, we compared the distribution of RM systems in 59 complete genome sequences. In S. pyogenes, the distribution of Type II methyltransferase (MTase) gene in S. pyogenes varied widely even among closely related strains. It could be divided into two groups of Type II methylases distribution, which is a prophage-dominant group and a CRISPR-dominant group. Also, some highly variable Type II MTases were found on the prophage region. Interestingly, some CRISPR spacers from the eight strains have high similarity with six MTases in the 59 S. pyogenes genomes. In addition, the number of MTases encoded on prophages in the prophage-dominant group is higher than that in the CRISPR-dominant group. Our study suggests the host bacteria actively incorporates phages containing MTase, although it has been considered that the phages encode MTases to avoid the host defense mechanism like RM system. Furthermore, CRISPR may be used to control prophage invasion. In conclusion, Type II MTase and prophage would play an essential role in the genomic diversification of S. pyogenes, and an evolutionary arms race between phages and bacteria also exists in S. pyogenes.