FIG. 7.

Germination of heat-activated B. subtilis spores with various levels of the GerB* receptor. Heat-activated (75°C) spores of B. subtilis strains FB10 (A) (wild-type GerB* levels), PS3502 (B) (20-fold-elevated GerB* levels), and PS3415 (C) (200-fold-elevated GerB* levels) were germinated at 30°C with various l-asparagine concentrations, and the percentages of germination of individual spores in various time intervals were determined as described in Materials and Methods using method B. The symbols used (and the percentage of spores that had germinated in 90 min and total number of spores analyzed) are as follows: panel A, ○, 1 mM l-asparagine (93% of 558 spores), •, 0.3 mM l-asparagine (75% of 425 spores), and ▵, 75 μM l-asparagine (46% of 445 spores); panel B, ○, 1 mM l-asparagine (99% of 631 spores), •, 50 μM l-asparagine (75% of 437 spores), and ▴, 10 μM l-asparagine (28% of 678 spores); panel C, ○, 1 mM l-asparagine (99% of 525 spores), •, 50 μM l-asparagine (90% of 341 spores), ▵, 8.25 μM l-asparagine (73% of 405 spores), and ▴, 6 μM l-asparagine (24% of 435 spores). In panels B and C, use of 5 mM l-asparagine gave nearly identical results to those with 1 mM l-asparagine (data not shown). In the absence of l-asparagine, there was ≤1% germination of PS3415 and PS3502 spores in 120 min, although the preparation of FB10 spores used in this experiment exhibited ∼6% germination in 120 min in the absence of l-asparagine, and this was corrected for in the data used in panel A. Note that (i) the values given on the vertical axis are the percentage of spores that germinated in a particular 5- or 10-min period in the experiment and (ii) the latter values have been normalized to the total number of spores that germinated in the complete experimental period.