FIG. 3.

Northern blot hybridization analysis of the varS transcripts during cultivation of S. virginiae (A) and for virginiamycin-induced mRNAs (B). (A) Total RNA was extracted from cells cultivated for the indicated times (hours) at 28°C. RNA (10 μg) was loaded in each lane, electrophoresed on a 1.2% agarose gel, and transferred to Hybond-N+ (Amersham Pharmacia Biotech) according to the manufacturer’s recommendations. Hybridization was carried out at 65°C for 20 h with the varS probe (Fig. 2A). VB and virginiamycin production under the experimental conditions started at 11 and 13 h of cultivation, respectively. (B) RNAs from cells without any addition or with either VM₁ (10 μg/ml) or VS (10 μg/ml) added at 8 h and harvested at 9, 10, or 11 h of cultivation were analyzed. Probe and hybridization conditions were the same as those used for panel A.