TABLE 2.

Yields of Erm^s isolates among Str^r colonies after transformation^a

rpsL,erm marked gene deletion	Yield of Strs Ermr (rpsL,erm) derivative of recipient strain ± SD:
	26695-str	SS1-str	X47	G27MA-str
mdaB	0.84 ± 0.13 (9)	0.40 ± 0.10 (2)	0.88 ± 0.14 (2)	0.21 ± 0.14 (4)
frxA	0.53 ± 0.22 (10)	0.90 ± 0.04 (2)	0.87 ± 0.03 (2)	0.17 ± 0.15 (4)
fur	0.28 ± 0.3 (8)	0.22 ± 0.11 (2)	0.71 ± 0.03 (2)	0.56 ± 0.26 (4)
nikR	0.54 ± 0.42 (2)	0.86 ± 0.18 (2)	0.96 ± 0.02 (2)	0.38 ± 0.35 (4)

^aAverage fraction of Str^r colonies ± standard deviation that were Erm^s after transformation of the indicated rspL,erm cassette containing recipient strain with isogenic wild-type genomic DNA. These Erm^s colonies were products of transformation and replacement of the contraselectable cassette, not gene conversion. These fractions are based on erythromycin resistance tests of approximately 30 colonies per transformation experiment. Listed in parentheses are the numbers of independent transformations, each with a different single colony isolate of the indicated recipient strain.