TABLE 3.

¹³C enrichments at individual carbon positions of amino acids from I. hospitalis (15), from mixed cells of the coculture of I. hospitalis and N. equitans, and from purified N. equitans cells after cultivation in the presence of [1-¹³C]acetate^a

Amino acid	Position	Relative 13C concn (%)
		I. hospitalis	Coculture	N. equitans
Alanine	1	NDb	1.1	ND
	2	16.8	3.3	3.1
	3	3.3	1.2	1.1
Serine	1	ND	ND	ND
	2	15.3	2.3	3.8
	3	3.3	1.1	1.1
Aspartate	1	1.1	ND	ND
	2	14.5	3.6	4.3
	3	4.6	1.1	1.1
	4	1.1	ND	ND
Threonine	1	ND	1.7	ND
	2	14.0	4.5	7.8
	3	3.3	1.9	2.2
	4	1.1	1.1	1.1
Glutamate	1	20.0	8.7	++c
	2	3.3	1.9	1.1
	3	16.9	8.2	7.8
	4	5.7	2.3	1.8
	5	1.1	1.1	ND
Lysine	1	22.6	5.6	10.7
	2	76	2.2	2.8
	3	6.9	1.8	1.8
	4	26.3	4.2	6.7
	5	7.7	1.5	1.7
	6	1.1	1.1	1.1

^aThe values shown were determined from a single experiment by quantitative nuclear magnetic resonance spectroscopy. On this basis, we could not determine error margins. However, by comparison with other studies using quantitative nuclear magnetic resonance spectroscopy, the errors can be estimated to be around ±25% of the listed values. Due to possible different relaxation behaviors of the reference (i.e., unlabeled material) and the bioenriched samples, the errors can be even higher for quaternary carbon atoms (for example, C-1 of lysine). Strong ¹³C enrichments are in boldface.

^bND, not detected.

^c++, high signal intensity.