Unusual organization of the 23S rRNA genes in the Rhizobiaceae

The presence of intervening sequences (IVSs) in the 23S rRNA genes of rhizobia and the phenomenon of fragmentation of their matured 23S-like rRNA molecules are analysed. A novel IVS-IVS II, in the 23S rRNA gene of several rhizobial strains is described, which is located approximately at position 540 bp (E. coli numeration). In contrast to the recently published IVS I occurring at position 130 of the gene, which was shown to be a common feature for all representatives of the family Rhizobiaceae, the IVS II was found only in a limited number of strains.