Fig. 1. Pattern of des–lacZ expression in wild-type and yocF^–yocG^– cells before and after temperature downshift. (A) Bacillus subtilis AKP3 cells (circles) and AKP21 cells (triangles) harbouring a des–lacZ transcriptional fusion were grown at 37°C to an optical density of 0.35 (at 525 nm) and then divided into two samples. One sample was transferred to 25°C (filled symbols), and the other was kept at 37°C (open symbols). Specific β-gal activities were determined at the indicated time intervals. (B) Bacterial strains [wild-type AKP3 (wt), yocF^–yocG^– (AKP21), yocF^–yocG^– pXyl:yocFG (AKP2147), yocF^–yocG^– pXyl:yocG (AKP2152), yocG^– (AKP9) and yocG^– pXyl:yocG (AKP952)] were streaked onto Luria–Bertani (LB) medium containing 30 µg/µl X-Gal, with (shaded quarter) or without (empty quarter) the addition of 0.8% l-xylose. The strains were incubated at 37°C for 12 h (left column) or for 5 h at 37°C, and then transferred to 25°C for 36 h (right column) before photography.