TABLE 6.

Concentrations of nutrient germinants required to stimulate 50% spore germination in strains with substituted GerVB^a

Strain	Relevant genotypec	K0.5(germ) (mM)b
		Glucose	Proline	Leucine
GC500	gerU negative	NAd	NA	NA
GC501	gerU positive (gerUA-gerUC-gerVB)	0.33	0.34	49
GC503	gerUA-gerUC	NA	NA	NA
GC509	GerVB E196Q	72	NA	100
GC510	GerVB E196D	55	NA	NA
GC525	GerVB Y191A	33	18	NA
GC526	GerVB F192A	25	127	ND (21)e
GC515	GerVB P193A	16	30	34
GC517	GerVB P343A	72	ND (23)	NA

^aSpores were germinated in 5 mM Tris-HCl, pH 7.8, for 90 min with various concentrations of glucose (10, 25, 50, 100, 175, 250, 400, 600, 800, and 1,000 mM), proline (25, 50, 75, 100, 150, 200, 250, and 300 mM), and leucine (1, 5, 10, 20, 50, 80, 100, and 120 mM); and germination was monitored as described in Materials and Methods. Strain GC517 was additionally germinated in 1,200 and 1,400 mM glucose. Strain GC501 was germinated in more dilute solutions (0.1 to 10 mM) of glucose and proline.

^bThe concentrations of germinant required to stimulate 50% spore germination [K_0.5(germ)] were calculated after incubation for 60 min for glucose and proline, after which no further germination was observed, and 90 min incubation for leucine. The values presented for each strain are derived from three independent experiments conducted with the same spore preparation; similar values were obtained with other spore preparations. The calculated standard error associated with all measurements is less than 10%.

^cAll strains are ΔgerWB::Sp^r.

^dNA, not applicable (spore germination <5% after 90 min incubation).

^eND, not determined. Values in parentheses indicate the apparent rate of spore germination (in percent) after 90 min incubation at the highest concentration of germinant tested.