Table 3. Effect of the number of I-SceI sites on the counter-selection for large-scale deletion^a.

Mutantb	DR (bp)	The first double-crossoverc	Numbers of DSB	xylose induction concentrationd
				0%	0.5%	1.0%	2.0%
20.5 kb-DEL	1000	(4.5±0.1)×103	one-ended	(2.8±0.4)×10−7	(1.7±0.2)×10−6	(4.4±0.1)×10−6	(1.5±0.2)×10−5
			two-ended	(3.2±0.2)×10−7	(5.4±0.1)×10−6	(1.4±0.4)×10−5	(2.9±0.3)×10−5
75.9 kb-DEL	1000	(4.3±0.2)×103	one-ended	(2.5±0.3)×10−7	(1.5±0.4)×10−6	(4.6±0.1)×10−6	(1.1±0.3)×10−5
			two-ended	(3.0±0.2)×10−7	(6.0±0.3)×10−6	(1.0±0.2)×10−5	(2.6±0.1)×10−5

^aData are means ± SD from three independent experiments for genetic manipulations.

^b20.5 kb-DEL, large deletion of 20.5 kb DNA sequence (528148–548697 SubtiList coordinates) of BUK; 75.9 kb-DEL, large deletion of 75.9 kb DNA sequence (1781306–1857233 SubtiList coordinates) of BUK.

^cThe first double-crossover recombination efficiency was calculated as the number of Cm^R colonies/µg of dsDNA PCR product.

^dCounter-selection efficiency was calculated as Nr/Nt. Nr, number of 5FU^R Cm^S colonies in the culture treated by different concentration of xylose; Nt, number of total colonies in culture treated by different concentration of xylose.