title: Genome analysis of a novel Bradyrhizobium sp. DOA9 carrying a symbiotic plasmid.
abstract: Bradyrhizobium sp. DOA9 isolated from the legume Aeschynomene americana exhibited a broad host range and divergent nodulation (nod) genes compared with other members of the Bradyrhizobiaceae. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the nod gene-harboring soybean symbiont B. japonicum USDA110, whereas the plasmid showed highest similarity with pBBta01 of the nod gene-lacking photosynthetic strain BTAi1, which nodulates Aeschynomene species. Unlike in other bradyrhizobia, the plasmid of DOA9 encodes genes related to symbiotic functions including nodulation, nitrogen fixation, and type III/IV protein secretion systems. The plasmid has also a lower GC content (60.1%) than the chromosome (64.4%). These features suggest that the plasmid could be the origin of the symbiosis island that is found in the genome of other bradyrhizobia. The nod genes of DOA9 exhibited low similarity with those of other strains. The nif gene cluster of DOA9 showed greatest similarity to those of photosynthetic bradyrhizobia. The type III/IV protein secretion systems of DOA9 are similar to those of nod gene-harboring B. elkanii and photosynthetic BTAi1. The DOA9 genome exhibited intermediate characteristics between nod gene-harboring bradyrhizobia and nod gene-lacking photosynthetic bradyrhizobia, thus providing the evidence for the evolution of the Bradyrhizobiaceae during ecological adaptation. Bradyrhizobium sp. DOA9 isolated from the legume Aeschynomene americana exhibited a broad host range and divergent nodulation (nod) genes compared with other members of the Bradyrhizobiaceae. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the nod gene-harboring soybean symbiont B. japonicum USDA110, whereas the plasmid showed highest similarity with pBBta01 of the nod gene-lacking photosynthetic strain BTAi1, which nodulates Aeschynomene species. Unlike in other bradyrhizobia, the plasmid of DOA9 encodes genes related to symbiotic functions including nodulation, nitrogen fixation, and type III/IV protein secretion systems. The plasmid has also a lower GC content (60.1%) than the chromosome (64.4%). These features suggest that the plasmid could be the origin of the symbiosis island that is found in the genome of other bradyrhizobia. The nod genes of DOA9 exhibited low similarity with those of other strains. The nif gene cluster of DOA9 showed greatest similarity to those of photosynthetic bradyrhizobia. The type III/IV protein secretion systems of DOA9 are similar to those of nod gene-harboring B. elkanii and photosynthetic BTAi1. The DOA9 genome exhibited intermediate characteristics between nod gene-harboring bradyrhizobia and nod gene-lacking photosynthetic bradyrhizobia, thus providing the evidence for the evolution of the Bradyrhizobiaceae during ecological adaptation.
authors.affiliation: Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Okazaki
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Rujirek
authors.initials: R
authors.lastname: Noisangiam
authors.affiliation: Graduate School of Life Science, Tohoku University, Sendai, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okubo
authors.affiliation: Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Kaneko
authors.affiliation: Center of Omics and Bioinformatics, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Kenshiro
authors.initials: K
authors.lastname: Oshima
authors.affiliation: Center of Omics and Bioinformatics, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Masahira
authors.initials: M
authors.lastname: Hattori
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Kamonluck
authors.initials: K
authors.lastname: Teamtisong
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Pongpan
authors.initials: P
authors.lastname: Songwattana
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Panlada
authors.initials: P
authors.lastname: Tittabutr
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Nantakorn
authors.initials: N
authors.lastname: Boonkerd
authors.affiliation: Department of Biological Sciences, Faculty of Science, Kyousei Science Center for Life and Nature, Nara Women's University, Kitauoya Nishimachi, Nara 630-8506, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Saeki
authors.affiliation: Graduate School of Life Science, Tohoku University, Sendai, Japan.
authors.forename: Shusei
authors.initials: S
authors.lastname: Sato
authors.affiliation: Graduate School of Science and Engineering, Kagoshima University, Kagoshima, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uchiumi
authors.affiliation: Graduate School of Life Science, Tohoku University, Sendai, Japan.
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Neung
authors.initials: N
authors.lastname: Teaumroong
mesh_terms: D001483:Base Sequence; D020369:Bradyrhizobium / Q000145:classification / Q000235:genetics*; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D009586:Nitrogen Fixation / Q000235:genetics; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013559:Symbiosis