title: An Active Type I-E CRISPR-Cas System Identified in Streptomyces avermitilis.
abstract: CRISPR-Cas systems, the small RNA-dependent immune systems, are widely distributed in prokaryotes. However, only a small proportion of CRISPR-Cas systems have been identified to be active in bacteria. In this work, a naturally active type I-E CRISPR-Cas system was found in Streptomyces avermitilis. The system shares many common genetic features with the type I-E system of Escherichia coli, and meanwhile shows unique characteristics. It not only degrades plasmid DNA with target protospacers, but also acquires new spacers from the target plasmid DNA. The naive features of spacer acquisition in the type I-E system of S. avermitilis were investigated and a completely conserved PAM 5'-AAG-3' was identified. Spacer acquisition displayed differential strand bias upstream and downstream of the priming spacer, and irregular integrations of new spacers were observed. In addition, introduction of this system into host conferred phage resistance to some extent. This study will give new insights into adaptation mechanism of the type I-E systems in vivo, and meanwhile provide theoretical foundation for applying this system on the genetic modification of S. avermitilis.
authors.affiliation: Department of Microbiology, College of Biological Sciences, China Agricultural University, Beijing, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: Department of Microbiology, College of Biological Sciences, China Agricultural University, Beijing, PR China.|State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Microbiology, College of Biological Sciences, China Agricultural University, Beijing, PR China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Microbiology, College of Biological Sciences, China Agricultural University, Beijing, PR China.
authors.forename: Yajie
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Microbiology, College of Biological Sciences, China Agricultural University, Beijing, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Song
mesh_terms: D064113:CRISPR-Cas Systems / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D013302:Streptomyces / Q000235:genetics*