Structure, synthesis, and post-transcriptional modification of ribosomal ribonucleic acid in Bdellovibrio bacteriovorus

Abstract

The structure, synthesis, and post-transcriptional modifications of 23-S and 16-S ribosomal RNAs (rRNAs) have been studied in the facultatively parasitic bacterium, Bdellovibrio bacteriovorus. The mature 23-S and 16-S type of rRNAs in Bdellovibrio are larger than the analogous molecules in Escherichia coli by at least 1.0 - 10(5) and 0.5 - 10(5) daltons, respectively, and have a conformation different from E. coli rRNAs as judged by relative electrophoretic mobilities in polyacrylamide gels with and without denaturing conditions. Studies on the kinetics of synthesis and maturation of ribosomal RNA in Bdellovibrio show that precursor forms analogous to p23-S and p16-S in E. coli are synthesized. In addition, some earlier precursor rRNAs in Bdellovibrio are seen that appear analogous to the 25S and 17.5-S pre-rRNAs that have only been observed in the RNAase III deficient mutant of E. coli strain AB301-105 (Nikolaev, Birenbaum, M. and Schlessinger, D. (1975) Biocheim, Biophys. Acta 395, 478-489). These early precursor stages have not been observed in other procaryotic species, including E. coli that have normal levels of RNAase III. The results from the Bdellovibrio system provide that the 25-s and 17.5-S pre-rRNAs are normal stages of rRNA modification and are part of a multiple step maturation process, and therefore are not aberrations associated with the RNase III deficient mutation.