Ji Lab Develops Bacterial Superbug Genome Editing Tool

The Ji Lab at The School of Physical Science and Technology has developed a CRISPR/Cas9-based system (pCasSA) for rapid andefficient genome editing in Staphylococcusaureus, a major human pathogen that causes serious infections with a highmortality rate. Their work was recently published online in the Journal of the American Chemical Society in a paper titled “Rapid and Efficient Genome Editing in Staphylococcus aureus by Using an Engineered CRISPR/Cas9 System.” Dr. Chen Weizhong is the first author and first-year graduate student Zhang Yifei is the second author. Dr. Won-Sik Yeo and Professor Taeok Bae of Indiana University’s School of Medicine-Northwest arethe third and fourth authors, respectively and Professor Ji Quanjiang is the corresponding author. The group has submitted a patent application for this technique.

Staphylococcus aureus, a major human pathogen, can cause a variety of infectious diseases,ranging from minor skin infections to life-threatening diseases, such asnecrotizing pneumonia, endocarditis, pseudomembranous enterocolitis, septicemiaand toxic shock syndrome. Moreover, the emergence of antibiotic-resistant S. aureus, in particular the methicillin-resistant Staphylococcus aureus (MRSA, a superbug)has rendered infections with the highest mortality rate in the United Statessince 2007, emphasizing the dire need for novel treatment methods ofthese infections. Genome editing and screening techniques are the key means tounveil and study novel drug targets and thus may provide a way to counter S. aureus infections. 

The discovery of the CRISPR/Cas9 system provides a simple, sequence-specific platform forgenerating a double-strand DNA break in the target genome, enabling precise genome editing. By engineering the CRISPR/Cas9 system to be adaptable in S. aureus, the Ji Lab has developed a CRISPR/Cas9-mediated genome editing tool (pCasSA) in S. aureus for the first time in this organism. The method is capable of rapidly editing the genomes of a variety of S. aureus strains, including the RN4220, Newman, and USA300 (MRSA) strains, with high efficiencies. The pCasSA system was further engineered to bea highly efficient transcription-inhibition system, an effective tool for fast and accurate screening of genes and unexplored drug targets in S. aureus.

Thistechnique will greatly reduce the time and effort needed for genome editing in S. aureus. Further utilizations andoptimizations of this tool should dramatically accelerate a wide variety ofinvestigations in S. aureus andrelated organisms, such drug development, enzymology, natural product mining,gene characterization, and other basic science research in microbiology as well as interdisciplinary research in chemical biology and synthetic biology.

This work was financially supported by ShanghaiTech Startup Funding and the NIH (AI121664 to T.B.).

Read more at: http://pubs.acs.org/doi/abs/10.1021/jacs.6b13317

Crystalstructure of the Cas9 protein and the scheme of CRISPR/Cas9-mediated genome editing.

CRISPR/Cas9-mediatedgenome editing in S. aureus. (a) The scheme of editing procedures. (b) pCasSA-mediated disruption of cntA gene in the RN4220 strain.

Group members of the Ji Lab: First from right, Chen Weizhong (first author); Second from left, ZhangYifei (second author); First from left, Ji Quanjiang (corresponding author).