TABLE 3.
Effect of Ca2+–DPA treatment on the heat resistance of wild-type and mutant sporesa
| Genotype (strain) and germination medium | Titer (CFU/ml/OD600 unit)b of spores
|
|
|---|---|---|
| Unheated | Heated | |
| Wild type (PS832) | ||
| Water | 6.5 × 107 | 4.5 × 107 |
| Ca2+–DPA | 6.5 × 107 | 4.5 × 106 |
| ger mutantc (FB85) | ||
| Water | 2.1 × 105 | 8 × 105 |
| Ca2+–DPA | 5.7 × 107 | 2.4 × 104 |
a
Spores were heat activated, incubated in water or 60 mM Ca2+–DPA for 60 min at room temperature, either heated (at 70°C for 1 h) or not heated, plated on LB agar, and incubated overnight at 37°C prior to colony counting.
b
The titers represent the means of two different experiments, and the values in these two experiments were within 40% of each other. Similar values were also obtained using two different preparations of spores.
c
The ΔgerA::spc ΔgerB::cat ΔgerK::ermC ΔyndDEF::tet ΔyfkQRT::neo mutant was used.