title: Bacterial clade with the ribosomal RNA operon on a small plasmid rather than the chromosome.
abstract: 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 clade within the genus Aureimonas. Our finding introduces a previously unaddressed viewpoint into studies of genetics, genomics, and evolution in microbiology and biology in general.
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Mizue
authors.initials: M
authors.lastname: Anda
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ohtsubo
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okubo
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sugawara
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nagata
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Tsuda
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan kiwamu@ige.tohoku.ac.jp hmitsui@ige.tohoku.ac.jp.
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan kiwamu@ige.tohoku.ac.jp hmitsui@ige.tohoku.ac.jp.
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Mitsui
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics*; D009876:Operon; D010957:Plasmids / Q000235:genetics*; D012329:RNA, Bacterial / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*
chemical_list: D012329:RNA, Bacterial; D012335:RNA, Ribosomal
keywords: Aureimonas; chromosome; genome rearrangement; plasmid; ribosomal RNA operon