TABLE 4.

β-Galactosidase activities of nasD-lacZ fusions in wild-type and mutant strains grown under aerobic conditions

Nitrogen sourcea	β-Galactosidase activity (Miller units)b
	LAB2854 (wild type)	LAB2862 (ΔresDE)	LAB2863 (fnr)	LAB2911 (tnrA)
Glutamate	14	13	20	0.4
Nitrate	40	21	43	0.6
Nitrite	88	29	84	<0.1
Ammonium	0.7	0.6	0.6	0.4
Nitrate plus ammonium	1.2	NEc	NE	NE
Nitrite plus ammonium	2.3	NE	NE	NE

^aCells were grown aerobically in TSS minimal medium with 0.5% glucose containing the indicated nitrogen sources. 

^bMaximum activities during growth are shown (averages of three or more experiments). The standard error was less than 25%. 

^cNE, not examined.