Title: Studies on rDNA from the extreme thermophilic eubacterium <i>Thermus thermophilus</i> HB8
Abstract: 23 S ribosomal ribonucleic acid gene from the extreme thermophile eubacterium Thermus thermophilus HB8 has been cloned in pBR322, and the nucleotide sequence of region D has been determined, which encompasses 873 nucleotides at the 3′‐end of the RNA. We compare the primary and secondary structure of this region with the respective part of the 23 S rRNA from Escherichia coli and Bacillus stearothermophilus . A high level of structural conservation can be observed, throughout the RNA domain, albeit the usage of G/C basepairs is substantial even in comparison with another thermophilic eubacterium B. stearothermophilus . It is surprising that, in contrast to the usage of 3′ U‐G 5′ , the occurrence of 3′ G‐U 5′ is comparable in E. coli as well as in B. stearothermophilus and T. thermophilus . Furthermore, it is most remarkable that the use of 3′ A‐U 5′ and 3′ U‐A 5′ is, compared to E. coli , only slightly reduced in B. stearothermophilus , but drastically decreased in T. thermophilus .