Table 1.

Comparison of two gene knockout methods ^a.

Compared points	pSC101ts-sacB method by Blomfield et al. [8]	λ-Red recombinase method by Datsenko et al. [14]
Recombination via	Two times of single crossover	One time of double crossover and FLP (flippase)–FRT recombination
Enzymes for recombination	endogenous enzymes	λ Gam, Bet, Exo, and flippase
Reliability	Low due to resolution of original gene organizations	High
Host requirements	Only recombination-proficient hosts	Any
Plasmid construction	Necessary	unnecessary
Transformation efficiency required	Low	High
Transformation procedures required	Once	Twice
Marker gene used for integration	Not retained	Not retained
Unnecessary genome arrangement	No	Yes, leaving an 81–85-bp “scar” sequence [19]
Bacteria proven to be applicable	E. coli [6–9], M. xanthus [10], C. glutamicum [11], Rhodococcus spp. [12], and P. putida [13]	E. coli [14], Salmonella spp. [15], M. tuberculosis [16], Streptomyces spp. [17], and B. subtilis [18]

^aAdvantageous features are shown in bold.