Table 2.

Sporulation efficiency of B. subtilisstrains carrying multicopy plasmidsa

PlasmidbInsertViable cell countSpore count% Efficiency of sporulation
pRM17rapE2.2 × 1082.3 × 10710.4
pSK43rapEpromoter4.2 × 1081.8 × 10842.8
pSK38rapE phrE3.9 × 1081.2 × 10830.7
pSK39phrE3.0 × 1081.1 × 10836.6
pSK40phrEpromoter4.0 × 1081.3 × 10832.5
pHT315Vector3.2 × 1081.2 × 10837.5
• a Representative of several independent experiments.

• b JH642 derivatives harboring the multicopy plasmids were grown for 46 h at 37°C in Schaeffer's sporulation medium with the addition of erythromycin at a concentration of 5 μg/ml.