Non-random fragmentation of ribosomal RNA in Helicobacter pylori during conversion to the coccoid form

The integrity of DNA and ribosomal RNAs in exponentially growing (bacillary) and ageing stationary phase (coccoid) cultures of Helicobacter pylori type strain CCUG 17874 was investigated. Extensive non-random fragmentation of rRNAs was observed during the conversion to the coccoid form. Beside a small proportion of full-length 16S and 23S rRNA that was always present, the majority of both 16S and 23S rRNA molecules showed distinct highly specific fragmentation patterns. The 16S rRNA fragmentation was characterised in detail by means of Northern blot and primer extension analysis. One cleavage site was located within the highly conserved U5 region (position about 920). The results could not be attributed to the presence of intervening sequences in the 16S and 23S rRNA genes.