A locus encoding variable defense systems against invading DNA identified in streptococcus suis

Masatoshi Okura, Takashi Nozawa, Takayasu Watanabe, Kazunori Murase, Ichiro Nakagawa, Daisuke Takamatsu, Makoto Osaki, Tsutomu Sekizaki, Marcelo Gottschalk, Shigeyuki Hamada, Fumito Maruyama

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Streptococcus suis, an important zoonotic pathogen, is known to have an open pan-genome and to develop a competent state. In S. suis, limited genetic lineages are suggested to be associated with zoonosis. However, little is known about the evolution of diversified lineages and their respective phenotypic or ecological characteristics. In this study, we performed comparative genome analyses of S. suis, with a focus on the competence genes, mobile genetic elements, and genetic elements related to various defense systems against exogenous DNAs (defense elements) that are associated with gene gain/loss/exchange mediated by horizontal DNA movements and their restrictions. Our genome analyses revealed a conserved competence-inducing peptide type (pherotype) of the competence system and large-scale genome rearrangements in certain clusters based on the genome phylogeny of 58 S. suis strains. Moreover, the profiles of the defense elements were similar or identical to each other among the strains belonging to the same genomic clusters. Our findings suggest that these genetic characteristics of each cluster might exert specific effects on the phenotypic or ecological differences between the clusters. We also found certain loci that shift several types of defense elements in S. suis. Of note, one of these loci is a previously unrecognized variable region in bacteria, at which strains of distinct clusters code for different and various defense elements. This locus might represent a novel defense mechanism that has evolved through an arms race between bacteria and invading DNAs, mediated by mobile genetic elements and genetic competence.

Original languageEnglish
Pages (from-to)1000-1012
Number of pages13
JournalGenome Biology and Evolution
Issue number4
Publication statusPublished - 1 Apr 2017
Externally publishedYes


  • Bacterial defense systems
  • Competence system
  • Mobile genetic elements
  • Streptococcus suis


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