Bacterial clade with the ribosomal RNA operon on a small plasmid rather than the chromosome

Mizue Anda, Yoshiyuki Ohtsubo, Takashi Okubo, Masayuki Sugawara, Yuji Nagata, Masataka Tsuda, Kiwamu Minamisawa, Hisayuki Mitsui

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


rRNA is essential for life because of its functional importance in protein synthesis. The rRNA (rrn) operon encoding 16S, 23S, and 5S rRNAs is located on the "main" chromosome in all bacteria documented to date and is frequently used as a marker of chromosomes. Here, our genome analysis of a plant-associated alphaproteobacterium, Aureimonas sp. AU20, indicates that this strain has its sole rrn operon on a small (9.4 kb), high-copy-number replicon. We designated this unusual replicon carrying the rrn operon on the background of an rrn-lacking chromosome (RLC) as the rrn-plasmid. Four of 12 strains close to AU20 also had this RLC/rrn-plasmid organization. Phylogenetic analysis showed that those strains having the RLC/rrn-plasmid organization represented one cladewithin the genus Aureimonas. Our finding introduces a previously unaddressed viewpoint into studies of genetics, genomics, and evolution in microbiology and biology in general.

Original languageEnglish
Pages (from-to)14343-14347
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number46
Publication statusPublished - 2015 Nov 17


  • Aureimonas
  • Chromosome
  • Genome rearrangement
  • Plasmid
  • Ribosomal RNA operon


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