FIG. 2.

Northern blot analysis of pdh expression. Analysis of RNA isolated from batch cultures. (A) RNA isolated from S. mutans UA159 during exponential growth (lanes i) and 20 h into stationary phase (lanes ii). Ten micrograms of RNA was loaded for each sample. Ethidium bromide staining (left side) was used to confirm equal loading of the genes. The blots (right side) are on a different scale. The probes used for each blot were for internal portions of the pdh operon genes (Fig. 1) and are indicated to the right of each blot. A probe for an exponential-phase gene bound to the RNA prepared from the parental strain confirmed the quality of the RNA (data not shown). (B) Comparison of RNA isolated from 20-h stationary-phase cultures of strain UA159 (i) and ΔpdhD mutant SL14043 (ii) and probed for pdhA. The positions of size markers (in kb) are indicated on the left side of the Northern blots.