FIG. 1.

des mRNA production before and after cold shock at 20°C and in the absence or presence of 0.2 mg of chloramphenicol per ml. (A) Northern blot analysis with formaldehyde-agarose gels was carried out as described in Materials and Methods. Total RNA was isolated from strain JH642 grown until mid-exponential phase at 37°C (lane 1), from cells shifted from 37 to 20°C at different times (lanes 2 to 8) and from cells grown continuously at 20°C (lane 9). Each lane contains 8 μg of total RNA. RNA blots were probed with a des-specific probe. After autoradiography, blots were stripped and reprobed with a B. subtilis 23S rRNA-specific probe. Autoradiographs of the resulting blots are shown. (B) Graph of the results shown in panel A. The densities of the bands corresponding to des mRNA and 23S rRNA for each lane were measured by a densitometer. The ratio of the intensities of 23S and des was used for the plot. (C) Northern blot analysis was performed as described for panel A. Cells were grown at 37°C until mid-exponential phase (lane 1) and then treated with chloramphenicol (200 μg/ml) for 15 min (lane 3) or then shifted to 20°C for 45 min in the absence (lane 2) or presence (lane 4) of chloramphenicol (200 μg/ml).