Table 4.

Utilization of various nitrogen sources by P. phymatum wild type, nifA, rpoN mutant, and rpoN complemented strains ¹.

Nitrogen Source (s)		Utilization of Nitrogen
	wt	nifA mt	rpoN mt	rpoN complemented
30 mM NH4Cl	+	+	+	+
0.5 mM NH4Cl	+	+	+	±
30 mM NO3−	+	+	-	+
15 mM CH4N2O	+	+	-	+

¹ Growth was assessed with at least two independent replicates by measuring the optical density at 600 nm after incubation in ABC minimal medium supplemented with several nitrogen sources for 30 h at 30 °C and 220 rpm. The “+” sign corresponds to OD₆₀₀ ≥ 0.6 for ammonium, ≥ 0.3 for nitrate, and ≥ 0.6 for urea; the “±” sign corresponds to OD₆₀₀ ≥ 0.4 for ammonium.