Abstract
Preparing the genetically modified organisms have required much time and labor, making it the rate-limiting step but CRISPR/Cas9 technology appearance has changed this difficulty. Although reports on CRISPR/Cas9 technology such as genome editing and CRISPR interference (CRISPRi) in eukaryotes increased, those in prokaryotes especially in Staphylococci were limited. Thus, its potential in the bacteriology remains unexplored. This is attributed to ecological difference between eukaryotes and prokaryotes. Here, we constructed a novel CRISPRi plasmid vector, pBACi for Staphylococcus aureus. The transformation efficiency of S. aureus was ~104 CFU/μg DNA using a vector extracted from dcm negative, which encoded one of DNA modification genes, E. coli. Further, pBACi was introduced into various clinical isolates including that not accepting the conventional temperature-sensitive vector. dcas9 in the vector was expressed throughout the growth phases of S. aureus and this vector decreased various gene mRNA expressions based on the crRNA targeting sequences and altered the knockdown strains’ phenotypes. The targeted genes included various virulence and antibiotic resistant genes. Bioinformatics suggest this vector can be introduced into wide range of low-GC Gram-positive bacteria. Because this new CRISPR/Cas9-based vector can easily prepare knockdown strains, we believe the novel vector will facilitate the characterization of the function of genes from S. aureus and other Gram-positive bacteria.
Highlights
Staphylococcus aureus is a member of the normal human bacterial flora but causes a variety of diseases including from mild conditions such as skin abscess to life-threatening diseases such as toxic shock syndrome [1, 2]
We chose pKAT as a framework of the shuttle vectors, because we confirmed that this plasmid could be introduced into the S. aureus clinical strain, which did not accept the previous TS-vector [33]
We used Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/Cas9 components from pCas9 [19]. We estimated that these components would work well, because these were originated from Streptococcus pyogenes, which are classified into low Gram-positive cocci, similar to S. aureus
Summary
Staphylococcus aureus is a member of the normal human bacterial flora but causes a variety of diseases including from mild conditions such as skin abscess to life-threatening diseases such as toxic shock syndrome [1, 2]. S. aureus clinical isolates often exhibit multi-drug resistance and the infections from these multi drug resistant S. aureus have been an issue for decades [3, 4]. S. aureus infects human and animals [5, 6]. S. aureus infects mammary glands in ruminants and causes mastitis.
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