title: Divergent nod-containing Bradyrhizobium sp. DOA9 with a megaplasmid and its host range.
abstract: Bradyrhizobium sp. DOA9, a non-photosynthetic bacterial strain originally isolated from the root nodules of the legume Aeschynomene americana, is a divergent nod-containing strain. It exhibits a broad host range, being able to colonize and efficiently nodulate the roots of most plants from the Dalbergioid, Millettioid, and Robinioid tribes (7 species of Papilionoideae). In all cases, nodulation was determinate. The morphology and size of DOA9 bacteroids isolated from the nodules of various species of Papilionoideae were indistinguishable from the free-living form. However, they were spherical in Arachis hypogaea nodules. GusA-tagged DOA9 also colonized rice roots as endophytes. Since broad-host-range legume symbionts often carry multiple replicons in their genome, we analyzed the replicons for symbiosis genes by electrophoresis. DOA9 carried two replicons, a chromosome (cDOA9) and single megaplasmid (pDOA9) larger than 352 kb. The genes for nodulation (nodA, B, C) and nitrogen fixation (nifH) were localized on the megaplasmid. Southern blot hybridization revealed two copies of nodA on the megaplasmid, single copies of nodB and C on the megaplasmid, and one copy each of nifH on the chromosome and megaplasmid. These results suggested that Bradyrhizobium sp. DOA9 may have the unusual combination of a broad host range, bacteroid differentiation, and symbiosis-mediating replicons.
authors.affiliation: Center for Scientific and Technological Equipment, Suranaree University of Technology.
authors.forename: Kamonluck
authors.initials: K
authors.lastname: Teamtisong
authors.forename: Pongpan
authors.initials: P
authors.lastname: Songwattana
authors.forename: Rujirek
authors.initials: R
authors.lastname: Noisangiam
authors.forename: Pongdet
authors.initials: P
authors.lastname: Piromyou
authors.forename: Nantakorn
authors.initials: N
authors.lastname: Boonkerd
authors.forename: Panlada
authors.initials: P
authors.lastname: Tittabutr
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
authors.forename: Achara
authors.initials: A
authors.lastname: Nantagij
authors.forename: Shin
authors.initials: S
authors.lastname: Okazaki
authors.forename: Mikiko
authors.initials: M
authors.lastname: Abe
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uchiumi
authors.forename: Neung
authors.initials: N
authors.lastname: Teaumroong
mesh_terms: D015139:Blotting, Southern; D020369:Bradyrhizobium / Q000145:classification* / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D058507:Host Specificity; D019684:Magnoliopsida / Q000382:microbiology*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008853:Microscopy; D009586:Nitrogen Fixation; D055170:Plant Root Nodulation; D010957:Plasmids; D053204:Root Nodules, Plant / Q000382:microbiology