Precursors of 5 S ribosomal RNA in Bacillus subtilis

Bacillus subtilis 168 accumulates subnormal quantities of mature 5 S ribo-somal RNA in the presence of inhibitors of protein synthesis, such as chloramphenicol, or during pulse-labeling experiments. However, two RNA species, evidently precursors of m5 rRNA and therefore designated as p5 A and p5 B, do accumulate under these conditions. These RNA species are substantially longer than B. subtilis m5 rRNA: p5 A is about 179 nucleotides in length and p5 B is composed of approximately 152 nucleotides. The sum of p5 A, p5 B and m5 rRNA accumulating in the absence of protein synthesis, less excess chain length associated with p5 A and p5 B, equals the expected quantities of m5 rRNA in growing cells. p5 A and p5P B both contain all t 1 RNase-generated oligonucleotides characteristic of m5 rRNA plus additional sequences. At least the 5′ termini of p5 A and p5 B differ from that of m5. If chloramphenicol is removed from a culture in which p5 A and p5 B have accumulated and further RNA synthesis is inhibited, then a quantitative reciprocal loss of p5 A and p5 B occurs as m5 rRNA accumulates. No evidence suggests any p5 A to p5 B transition under these conditions.