Table 2.

Sporulation of strains of B. subtilis

Strain (relevant genotype)MediumaT26viable cells (CFU ml−1)T26spores (CFU ml−1)bSporulation (%)c
168 (wild-type)MM3.0 × 108 1.9 × 108 63
S1d 5.9 × 107 1.0 × 107 16
S1 + acetoin1.5 × 108 4.1 × 107 27
BSF45 (Pytr::pMUTIN2mcs)MM2.1 × 108 3.7 × 107 18
S15.4 × 107 3.0 × 106 5.5
S1 + acetoin3.0 × 107 5.0 × 105 1.7
BFS47 (ytrF-pMUTIN2mcs)MM3.2 × 108 2.0 × 108 62
S12.2 × 107 2.0 × 106 9.1
S1 + acetoin1.1 × 108 1.7 × 107 15
FU349 (ytrF::pMUTIN2mcs)MM1.2 × 108 2.5 × 107 21
S13.3 × 107 3.0 × 106 8.9
S1 + acetoin3.1 × 107 2.2 × 106 7.0
  • a Cells were grown until 2 h after the end of exponential growth (T 2) in MM at 37°C with shaking, and then the culture was divided into three parts. The cells in the first part were allowed to grow continuously in MM until T 26. The cells in the second and the third parts were harvested once, washed and resuspended in S1 medium in the presence and absence of acetoin, respectively, and grown untilT 26.

  • b Sporulation was quantified by measuring survival after incubation at 70°C for 15 min. The number of CFU was determined by spreading the cells onto TBABG containing erythromycin when needed. Experiments were repeated three times for each strain and medium with similar results; representative results are presented.

  • c Sporulation frequency is relative to the viable cell amount at T 26 of each culture of the strains.

  • d S1 medium contained 10 mM glycine and was supplemented with 10 mM acetoin as indicated.