Fractionation of ribonucleic acid transcripts synthesized during spore germination in Bacillus subtilis

Transcription was found to proceed stepwise during germination of Bacillus subtilis spores. Three distinct phases were evident with respect to pulse-labelled RNA synthesis and the RNA species synthesized. At the early stage of germination (Gm 1:0-15 min), RNA synthesis started in about 5 min and increased linearly when 1 min pulse-labelling with 3H-uridine was used. RNA molecules of relatively low molecular weight (LMW) 4S, 4.5S, 5S, LMW I, II, III, VII RNAs and so on were mainly synthesized during this stage. The relative synthesis of 16S and 23S rRNA was suppressed considerably at Gm 1. This suppression was eliminated by the mid stage of germination (Gm 2:15 to 40 min). Pulse-labelled RNA synthesis took on a constant level for about 20 min (Gm 2). The relative amounts of LMW I, II, III and VI RNAs in an aliquot (10,000 cpm) decreased at Gm 2. Gm 2 was followed by a tremendous increase in the pulse-labelled RNA synthesis (Gm 3 and outgrowth). The transition from Gm 1 to Gm 2 was inhibited by chloramphenicol. LMW I, III, and VI RNAs were densely banded at Gm 2 on administration of chloramphenicol. These results strongly suggested that transcription may be positively regulated at an early stage of germination. Possible positive factor(s) involved in this regulation are discussed.