FIG. 4.

Induction in different phases of growth. BCG^S(pG4697-6) was subcultured by performing a 1:100 dilution of an actively growing culture. Serial aliquots were removed at increasing OD₅₉₀ and split into paired subcultures. One subculture of each pair was not treated with antibiotics (●); the other subculture of each pair was treated with ethambutol at a final concentration of 5 μg/ml (□). After an additional 24 h, β-galactosidase activity was measured. β-Galactosidase units are shown as a function of the OD₅₉₀ of the paired subcultures at the time that they were removed from the parent culture.