TABLE 3.

Efficiency of recovery of fdxA::cat (null) transformants depends on bacterial genotype

Frequency of recovery of fdxA null transformants	Fraction of strains	Examples
Type I strains
Readily obtaineda	3 of 32	26695, Ind121, HUPB57
Obtained with difficultyb	3 of 32	Lit055, CPY6271, HUPB48
Obtained only after frxA inactivation	4 of 20	Ind27, Ind66, Chen13, Lit050
Not obtained after frxA inactivationc	16 of 20	Variousd
Obtained only after frxA and rdxA inactivation	1 of 2	HK192e
Type II strains
Readily obtained	20 of 23	SS1, 98QM3, 88-3887 and othersf
Not obtained	3 of 23	X47, HK152, R10

^aReadily obtained indicates that the yield of Cam^r fdxA null transformants was similar to that of Kan^r frxA null transformants generated with frxA::aphA DNAs in the same transformation mix.

^bObtained with difficulty indicates that the yield of Cam^r fdxA null transformants was <1% that of Kan^r frxA null transformants generated in the same transformation mix. In these cases, some Cam^r transformants did not contain allelic replacements of the wild-type fdxA allele by the null mutant allele and thus may have resulted from illegitimate recombination or some other mutation event.

^cNot obtained also indicates that the yield of Cam^r fdxA null transformants was <1% that of Kan^r frxA null transformants generated in the same transformation mix. We do not know if the not obtained class differs from the obtained with difficulty class.

^dThese strains were TN2, GS3, HPK5, CPY6261, and CPY6311 (Japan); HUPB63, HUPB71, HUPB72, and HUPB77 (Spain); A-11, A-13, and O76 (Lithuania); Ind92 and Chen5 (India); HK192 (HongKong); and PeCan9a (Peru).

^eIncorporation of frxA::aphA and rdxAΔ111 null mutations into HK192 allowed recovery of slow-growing fdxA null transformants in high yield, whereas incorporation of these mutations into PeCan9a did not allow fdxA null transformants.

^fThese additional strains were Lit5, Lit28-1, Lit43, Lit66-1, Lit75-1, Lit102, Lit113, Lit119, Lit120, Lit122, Alas219, Alas381, Alas10103, 2600, 2667, 2714, and Ind31.