TABLE 3.

Assimilation of two organic substrates simultaneously by RPAO in different plants, as determined by MAR

Unlabeled substrates	Radioactive tracer	Electron acceptor	Substrate uptake by RPAOa
			AAE WWTP	Egaa WWTP	Skagen WWTP
Acetate (1.5 mM) + propionate (1.5 mM)	[3H]acetate (Na)	Not addedb	+	+	+
Acetate (3.0 mM) + propionate (0.5 mM)	[1-14C]propionate (Na)	Not added	+	+	+
Acetate (1.5 mM) + butyrate (1.5 mM)	[1-3H]butyric acid	Not added or O2	−	−	−
Acetate (1.5 mM) + thymidine (1.5 mM)	[methyl-3H]thymidine	Not added or O2	+	+	+
Acetate (1.5 mM) + leucine (1.5 mM)	[4,5-3H]leucine	Not added or O2	+	+	+

^a+, radioactive substrate taken up; −, radioactive substrate not taken up.

^bNot added indicates anaerobic conditions.