FIG. 3.

Induction of σ^B by phosphate limitation or ethanol treatment in Rel^+/− B. subtilis. BSA46 (RelA⁺ □, ▪) or BSZ5 (RelA⁻ ○, •) were grown in a synthetic medium containing 0.15 mM (▪, •) or 0.6 mM (□, ○) PO₄ (panel A) or 0.05% (▪, •) or 0.2% (□, ○) glucose (panel B). Samples were taken at 30-min intervals and assayed for σ^B-dependent β-galactosidase activity. The arrows show the times at which the cultures left exponential growth. In panels C and D, BSA46 (C) and BSZ5 (D) were grown continuously in LB (≤) or exposed to 4% ethanol (▪, •) at the point indicated by the arrows. Vertical axes, β-galactosidase (Miller units). Horizontal axes, time (30-min intervals).