TABLE 1.

β-Galactosidase activities directed by the FF-melR promoter in the presence of plasmids expressing FnrP (pFnrP) and FNR (pGS24)

Strain	β-Galactosidase activitya
	Plasmid	Rich medium		Minimal medium
		Aerobic	Anaerobic	Aerobic	Anaerobic
JRG1728	pFnrP	14 ± 2	647 ± 13	95 ± 7	1,705 ± 119
JRG1728 iscS::kan	pFnrP	4 ± 1	24 ± 2	6 ± 1	323 ± 55
JRG1728	pGS24	507 ± 39	3,211 ± 260	440 ± 19	3,085 ± 75
JRG1728 iscS::kan	pGS24	77 ± 10	1,813 ± 68	77 ± 10	1,641 ± 258

^aActivities were measured in duplicate on at least three independently grown cultures; means ± standard errors are shown. Growth of cultures was aerobic or anaerobic, in either L broth, or M9 minimal medium, as indicated. E. coli JRG1728(pRW2A/FF) and JRG1728 iscS::kan (pRW2A/FF) were transformed with plasmids expressing FnrP (pFnrP) and FNR (pGS24). Units of β-galactosidase are as defined by Miller (18).