(*contributed equally to this work) 发布: 2018年01月20日第8卷第2期 DOI: 10.21769/BioProtoc.2688 浏览次数: 27267
评审: David CisnerosAlba BlesaTomas Aparicio
Abstract
With the recent implementation of the CRISPR/Cas9 technology as a standard tool for genome editing, laboratories all over the world are undergoing one of the biggest advancements in molecular biology since PCR. The key advantage of this method is its simplicity and universal applicability for species of any phylum. Of particular interest is the extensively studied Gram-negative bacterium Escherichia coli, as it is considered as the workhorse for both research and industrial purposes. Here, we present a simple, robust and effective protocol using the CRISPR/Cas9 system in combination with the λ Red machinery for gene knockout in E. coli. Crucial in our procedure is the use of a double-stranded donor DNA and a curing strategy for removal of the guide RNA encoding plasmid that allows starting a new mutation after only two working days. Our protocol allows multiple, stepwise gene knockout strains with high mutagenesis efficiencies applicable for high-throughput approaches.
Keywords: Biotechnology (生物技术)Background
The Gram-negative bacterium Escherichia coli is one of the most important organisms for biotechnological engineering. It has been successfully implemented in a wide range of processes in different sectors of industry, such as energy, agriculture, food production, biotechnology, and medicine. The biotechnology sector is improving fast due to a constant technological progress. In particular, the CRISPR/Cas9 technology is probably the biggest revolution in (molecular) biology since PCR (Ledford, 2015). Briefly, CRISPR/Cas9 protects bacteria from invasive genetic elements such as plasmids and viruses (Marraffini, 2015). Taking advantage of this kind of acquired immune system from prokaryotes, a remarkably powerful tool for genome editing based on the CRISPR/Cas9 systems has been developed (Jinek et al., 2012).
The CRISPR/Cas9 system consists of a guide RNA (gRNA) and the endonuclease Cas9 both forming a complex in a way that directs the enzyme to the target site that is complementary to the gRNA promoting site-specific cleavage (Sander and Joung, 2014). The enzymatically generated double strand break (DSB) is being subsequently repaired by the cell through either homologous recombination (HR) or non-homologous end joining (NHEJ) (Iyama and Wilson III, 2012). However, NHEJ works poorly in E. coli (Shuman and Glickman, 2007; Wright et al., 2016) and thus genome editing protocols cannot rely on such a mechanism for this Gram-negative bacterium. Therefore, most approaches aiming to modify chromosomal DNA in E. coli exploit the phage recombinase-mediated homologous recombination (recombineering) using either the Rac prophage system (Zhang et al., 1998; Datta et al., 2006) or the three bacteriophage λ Red proteins Exo, Beta, and Gam (Murphy, 1998; Muyrers et al., 1999; Ellis et al., 2001). In fact, the presence of the λ Red machinery considerably increases mutagenesis efficiency as demonstrated in a recent study (Pyne et al., 2015), especially when combined with the CRISPR/Cas9 technology (Jiang et al., 2013).
Our laboratory established a robust, simple and rapid protocol for multiple, stepwise gene knockout in E. coli using the CRISPR/Cas9 technology in combination with the λ Red machinery (Zerbini et al., 2017). Here, we want to provide our genome editing protocol in detail, which results in high mutagenesis efficiencies and has the potential to be applied in high-throughput approaches.
Materials and Reagents
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文章信息
版权信息
© 2018 The Authors; exclusive licensee Bio-protocol LLC.
如何引用
König, E., Zerbini, F., Zanella, I., Fraccascia, D. and Grandi, G. (2018). Multiple Stepwise Gene Knockout Using CRISPR/Cas9 in Escherichia coli. Bio-protocol 8(2): e2688. DOI: 10.21769/BioProtoc.2688.
分类
微生物学 > 微生物遗传学 > 诱/突变
分子生物学 > DNA > 诱/突变
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