TABLE 3.
Heat-resistant spore formation by strains of B. subtilisa
| Strain (relevant genotype) | Asparagine | CFU (108)b
|
Ratio (%)c | |
|---|---|---|---|---|
| With heating | Without heating | |||
| 168 (wild type) | − | 4.4 | 5.3 | 83 |
| + | 3.4 | 4.3 | 79 | |
| FU340 (ΔasnB::neo) | − | 2.4 | 2.9 | 83 |
| + | 2.6 | 3.1 | 84 | |
| FU341 (ΔasnH::spc) | − | 3.5 | 4.4 | 80 |
| + | 2.8 | 3.7 | 76 | |
| FU342 (ΔasnO::cat) | − | NDd | 3.3 | ND |
| + | ND | 2.6 | ND | |
| FU346 (ΔasnB::neo ΔasnH::spc ΔasnO::cat) | − | ND | 2.6 | ND |
| + | ND | 2.4 | ND | |
Cells of each of the B. subtilis strains were inoculated into DSM with (+) and without (−) asparagine (50 μg/ml) and cultivated at 37°C for 24 h with shaking. The cultures were diluted appropriately and divided into two tubes; one was heated at 70°C for 15 min, and the other was not heated. Cells in each of the tubes were then spread onto TBABG plates containing antibiotics when needed, and the plates were incubated at 37°C for 16 h. Colonies that appeared on the plates were counted to calculate CFU.
Data from a single experiment are shown. The same experiments were repeated at least twice with similar results.
Ratio of CFU with heating to CFU without heating.
ND, not determined (<105 CFU).