A SINGLE RIBOSOMAL-RNA GENE REGION IN BRADYRHIZOBIUM-JAPONICUM

Bradyrhizobium japonicum contains only a single rRNA (rrn) gene region , despite its comparatively large genome size of 8,700 kb. The nucleot ide sequence revealed an organization of rRNA and tRNA genes that is f requently found in bacteria: 5'-rrs (16S rRNA)-ileT (tRNA(Ile))-alaT ( tRNA(Ala))-rrl (23S rRNA)-rrf (5S rRNA)-3'. The 5' end of the primary transcript, one of the 16S rRNA processing sites, and the 5' end of th e mature 16S rRNA were determined by primer extension. DNA hybridizati on experiments showed that the slowly growing Bradyrhizobium strains g enerally have only a single copy of the 16S rRNA gene, whereas the fas ter-growing Rhizobium species contain three rrs copies.