Zhengzhou University, China
Posters & Accepted Abstracts: J Med Microb Diagn
Escherichia coli has become one of the important model organisms for gaining insight into the molecular mechanisms associated with Type I CRISPR/Cas system function. It has been identified to only contain Type I-E and I-F system. However, due to the low incidence of Type I-F system in E. coli, the information on its diversity and immunity role is little known. In this study, we analyzed the occurrence and diversity of Type I-F system and explored its potential for typing strains in 1198 strains of B2 E. coli. We identified 413 strains harboring Type I-F CRISPR/Cas system and 9 strains containing Type I-E system. The components of Type I-F system, including repeat, spacer and cas genes, showed high conservation within single ST or between closely related STs. CRISPR spacer content and polymorphism were instrumental for differentiating highly closely related strain, such as ST141, ST998 and ST1159. The putative acquisition and deletion of spacers could reveal the evolution model between serotypes. The spacers showed more homology with plasmids than phages. The IncF1B-, IncFII- and IncI1-typing plasmids replicons was the predominant challenge for B2 strains, suggesting that Type I-F system may play an important role in the acquisition of antibiotic resistance. Collectively, our data provides one basis for better understanding the characterization and diversity of Type I-F system and its potential for genotyping strains.