Table 1.

EC₅₀ values (mm) for amino acids and the C. difficile spore

The averages and standard deviations for three biological replicates are shown. CND, could not determine; EC₅₀, concentration that achieves the half-maximum germination rate.

	C. difficile strain
	UK1 (wild type)	RS07 (alr2::ermB)	RS07 pRS89 (alr2::ermB palr2)
l-Alanine	5.5 ± 1.1	2.7 ± 1.8	10.7 ± 2.5
d-Alanine	11.5 ± 2.3	24.2 ± 6.6	6.6 ± 1.0
l-Serine	8.2 ± 0.8	2.5 ± 1.7	4.9 ± 0.5
d-Serine	7.8 ± 1.2	19.1 ± 5.0	CND