Table 2.

Development of CRISPR/Cas9 expression systems for genome engineering in bacteria.

Host	Endonuclease	Promoters	Guiding RNA	Function	Repair mechanism	Reference
C. beijerinckii	Cas9	spoIIE	sgRNA	Deletion	HR with double-stranded template	Wang et al., 2015
C. cellulolyticum	Cas9 (D10A)	P4 synthetic promoter	sgRNA	Deletion/insertion	NHEJ with double-stranded template	Xu et al., 2015
C. saccharoperbutylacetonicum	Cas9	PJ23119	gRNA	Deletion	HR with double-stranded template	Wang et al., 2017
E. coli	Cas9	S. pneumonia cas9 promoter	tracrRNA-crRNAa	Deletion	HR with double-stranded template	Jiang et al., 2013
E. coli	Cas9	J23119	sgRNA	Insertion/deletion	Lambda-Red HR and single-stranded template	Jiang et al., 2015
L. reuteri	Cas9	S. pneumonia cas9 promoter	tracrRNA-crRNA	Deletion	HR with single-stranded template	Oh and van Pijkeren, 2014
S. pneumonia	Cas9	S. pneumonia cas9 promoter	tracrRNA-crRNA	Deletion	HR with double-stranded template	Jiang et al., 2013
Streptomyces sp.	Cas9	rpsLp/rpsLp/gapdhp	sgRNA	Deletion	HR with double-stranded template	Cobb et al., 2015
Streptomyces sp.	Cas9	PtipA/J23119	sgRNA	Deletion	HR with double-stranded template	Huang et al., 2015
Streptomyces sp.	Cas9	PtipA	sgRNA	Deletion	NHEJ/HR with double-stranded template	Tong et al., 2015

^aDual expression of tracrRNA and crRNA.