[RNA synthesis during the stationary growth phase in the Bacillus subtilis Cgr4 mutant]

RNA synthesis was studied in Bacillus subtilis Cgr4 grown in the mineral sporulation medium enriched with glucose up to 2% and amino acids up to 1%. To study mRNA synthesis, a method of transfer of the 3H-uridine pulse-labeled culture to the supernatant of physiologically identical, not labeled culture, followed by further incubation was used, the amount of 3H-uridine in the supernatant as well as in cells being measured. RNA was also analysed electrophoretically and distribution of the label among the fractions was determined. It is shown that mRNA synthesized in the logarithmic phase degrades up to 12% on the 2nd hour of growth during 10 min; the mRNA in the stationary phase is stable on the 7th hour of growth; no degradation is observed in the course of 2-3 hours. The beginning of degradation coincides in time with secondary induction of the synthesis of serine proteases and with the onset of sharp decrease in incorporation of 3H-uridine in RNA as well as with induction of spore morphogenesis. On the basis of electrophoretical analysis of pulse-labeled RNA, it was demonstrated that, prior to the transfer, labeled uridine was included and preserved in RNA fraction for 2-3 hours after the transfer, this fraction corresponding in mobility with mRNA in polyacrylamide gel. The following conclusion may be drawn: stable mRNAs are synthesized in the stationary phase and may be used for the translation of extracellular serine protease.