Table 2.

EC₅₀ values for amino acids and C. difficile M68 spores.

Amino Acids	C. difficile M68
	EC50 (mM)
glycine	0.48 ± 0.2
L-arginine	3.6 ± 0.7
L-alanine	5.1 ± 0.7
taurine	7.7 ± 1.9
L-glutamine	10.1 ± 0.6
L-histidine	12.4 ± 5.8
L-lysine	18.5 ± 4.6
L-serine	19.4 ± 4.2
D-alanine	25.0 ± 6.6
D-serine	54.4 ± 2.6
D-lysine	56.9 ± 19.4
L-methionine	58.7 ± 4.6
L-threonine	59.8 ± 25.3
L-proline	73.2 ± 18.0
L-aspartic acid	425 ± 170
L-glutamate	CND
L-leucine	>500 mM
L-isoleucine	>500 mM
L-valine	>500 mM
L-phenylalanine	>500 mM
L-tyrosine	Not soluble
L-tryptophan	Not soluble
L-cysteine	Interfered with DPA measurements

EC₅₀ values were calcuated from the germination rate curves as described in the materials and methods. The values reported are the averages from three indepented experiments with the standard deviation from the mean.