TABLE 1.

Viability, Ca-DPA content, and core wet density of B. subtilis spores harvested after 2, 6, 15, 47, 51, 91, or 98 days^a

Spore age (days)	Viability (% of 2-day spores) on:		Ca-DPA content	Core wet density (g/ml)
	LB medium	Spz medium
2	100	100	100 ± 35	1.33
6	114	ND	ND	1.34
15	114	ND	ND	1.35
47	95	95	117 ± 16
51	ND	ND	ND	1.37
91	ND	ND	ND	1.39
98	105	121	123 ± 16	ND

^aSpores of B. subtilis harvested after various times and highly purified were tested for their viability on LB agar and Spizizen’s (Spz) minimal medium agarose plates as described in Materials and Methods. Ca-DPA content and core wet density were also measured as described in Materials and Methods. Values for 2-day spores’ viability and Ca-DPA content were set at 100%, and values for all older spores are expressed relative to the values for the 2-day spores determined in parallel. ND, not determined.