Table 1.

Expression of the lacZ fusions under different growth conditions

	β-Galactosidase activity, MUb
Plasmida	LBc	M9, Nitrogen Sufficientc	M9, Nitrogen Limitedc
pBR-σ54-lacZ-1	190	3,500	22,500
pBR-σ54-lacZ-2	140	400	800
pBR-lacZ-3	110	130	170

^a Plasmids were transformed into E. coli TG1 strain. ^b In Miller units [24]. ^c For growth conditions and β-galactosidase assay see Materials and Methods.