TABLE 4.

Effects of regulatory mutations on expression of a chromosomal Φ(nasR-lacZ) operon fusion

Straina	Genotypeb	β-Galactosidase sp actc with:		Ratio of sp act values
		NH4+, Gln	Gln
VJSK2507	Wild type	7	67	9.6
VJSK2520	rpoN::Km	15	22	1.5
VJSK2521	ntrC::Tn5	11	21	1.9
VJSK2588	−13/−12GC→AT	13	22	1.7
VJSK2531	−24G→A	8	14	1.8

^aDerivatives of strain VJSK2216 (Table 1). 

^bAll strains carry ΔrhaBS::[Φ(nasR-lacZ) {−469/+71}] (Fig. 1). 

^cDetermined as described in Materials and Methods and expressed in arbitary (Miller) units. Cultures were aerated in media containing the indicated nitrogen sources as described in Materials and Methods.