TABLE 5.

Investigation of dependence of pta expression on changing oxygen tension and nitrate as well as nitrite^a

Strain (relevant genotype)	Reporter gene fusion	β-Galactosidase activity (Miller units)b
		Aerobic	Anaerobic
			Fermentative	With nitrate	With nitrite
BSIP1104 (wild type)	Ppta-lacZ	210	185	200	200
MMB100 (ΔresDE)	Ppta-lacZ	180	175	170	170
MMB101 (fnr)	Ppta-lacZ	215	185	170	170

^aConstruction of the various B. subtilis strains carrying the indicated lacZ fusions is described in Materials and Methods. The indicated strains were grown either aerobically or anaerobically with 50 mM glucose as a carbon source and ammonia as a nitrogen source, with the indicated additions (10 mM with nitrate or nitrite), to the mid-exponential growth phase as outlined in detail before (8, 20). 

^bβ-Galactosidase activities were assayed as described before (16, 20). The results represent averages from of at least five independent experiments performed in triplicate, with a standard error of less than 10%.