Identification and functional study of type III-A CRISPR-Cas systems in clinical isolates of Staphylococcus aureus.
The CRISPR-Cas (clustered regularly interspaced short palindromic repeats [CRISPR]-CRISPR associated proteins [Cas]) system can provide prokaryote with immunity against invading mobile genetic elements (MGEs) such as phages and plasmids, which are the main sources of staphylococcal accessory genes. To date, only a few Staphylococcus aureus strains containing CRISPR-Cas systems have been identified, but no functional study in these strains has been reported. In this study, 6 clinical isolates of S. aureus with type III-A CRISPR-Cas systems were identified, and whole-genome sequencing and functional study were conducted subsequently. Genome sequence analysis revealed a close linkage between the CRISPR-Cas system and the staphylococcal cassette chromosome mec (SCCmec) element in five strains. Comparative sequence analysis showed that the type III-A repeats are conserved within staphylococci, despite of the decreased conservation in trailer-end repeats. Highly homologous sequences of some spacers were identified in staphylococcal MGEs, and partially complementary sequences of spacers were mostly found in the coding strand of lytic regions in staphylococcal phages. Transformation experiments showed that S. aureus type III-A CRISPR-Cas system can specifically prevent plasmid transfer in a transcription-dependent manner. Base paring between crRNA and target sequence, the endoribonuclease, and the Csm complex were proved to be necessary for type III-A CRISPR-Cas immunity.
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China.
Linyan
L
Cao
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China.
Chun-Hui
CH
Gao
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China.
Jiade
J
Zhu
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China.
Liping
L
Zhao
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China.
Qingfa
Q
Wu
Department of Laboratory Medicine, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200127, China.
Min
M
Li
CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China. Electronic address: sunb@ustc.edu.cn.
Baolin
B
Sun
D064113:CRISPR-Cas Systems; D023061:Gene Order; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D006801:Humans; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D014158:Transcription, Genetic; D014169:Transformation, Bacterial
Prophage; SCCmec; Staphylococcus aureus; Type III-A CRISPR-Cas system