FIG. 2.

Transcriptional regulation of flaB tested in S. solfataricus strain P2. (A) Northern analysis of flaB gene transcript after transfer of a cell culture from rich medium (TYS) to MM. RNA was isolated from cells before and 1 and 2 hours after the shift into either rich medium or MM. The flaB gene transcript was detected using a specific digoxigenin-labeled probe (top). The positions of the 16S and 23S ribosomal RNAs, determined by methylene blue staining of the blot membrane (bottom), are indicated. (B) Detection of flaB gene transcript levels at different growth stages by Northern analysis (top) and RT-PCR (middle). RNA was isolated from cells grown in rich medium to mid-logarithmic (L) or stationary (S) phase. Amounts of RNA identical to those used in the Northern blot analysis were separated on 1.5% agarose gels and stained with ethidium bromide (bottom). (C and D) Semiquantitative RT-PCR analysis of flaB expression levels in S. solfataricus cells either transferred from rich medium to MM (C) or grown on MM supplemented with a carbon source as indicated and harvested at an optical density of 0.6 (D). Samples for panel C were taken under conditions identical to those described for panel A. The upper panels show the PCR products, and the lower panels are a loading control for the RNA used in the RT-PCRs.