TABLE 1.

¹³C recoveries from propionate conversion by S. propionica and M. hungatei after 30 days of incubation^a

Isotope recovered	13C recovery (%) with a substrate:
	[1-13C]P	[2-13C]P	[3-13C]P	[2,3-13C]P	[2-13C]A
[1-13C]propionate	11
[2-13C]propionate	2	14		1
[3-13C]propionate	2		17	1	6
[1,2-13C]propionate	1	2
[2,3-13C]propionate	1			15
[1-13C]acetate	29	53		16
[2-13C]acetate	27	1	62	18	57
[1,2-13C]acetate	2	2		35
[1-13C]butyrate	4	9		3
[1,2-13C]butyrate				3
[2-13C]butyrate	5		9	1	9
[2,3-13C]butyrate	2			3
[3-13C]butyrate	3	10		1
[3,4-13C]butyrate				5
[4-13C]butyrate	4		13	2	10
Total	93	91	101	104	82

^aPropionate (P) was tested with label at the C1, C2, or C3 atom or double-labeled at the C2 and C3 atoms. Acetate (A) was introduced with label at the C2 atom. The inaccuracy of the quantified signals is usually >5% for methyl and methylene carbon atoms present at a concentration of at least 0.5 mM (values of >10% in the table). Quantification of signals present at lower concentrations and especially those of carboxylic acids is less accurate. However, the inaccuracy of those signals was usually only between 5 and 20%.