title: Predominant nifH transcript phylotypes related to Rhizobium rosettiformans in field-grown sugarcane plants and in Norway spruce.
abstract: Although some sugarcane cultivars may benefit substantially from biological nitrogen fixation (BNF), the responsible bacteria have been not identified yet. Here, we examined the active diazotrophic bacterial community in sugarcane roots from Africa and America by reverse transcription (RT)-PCR using broad-range nifH-specific primers. Denaturing gradient gel electrophoresis (DGGE) profiles obtained from sugarcane showed a low diversity at all sample locations with one phylotype amounting up to 100% of the nifH transcripts. This major phylotype has 93.9-99.6% DNA identity to the partial nifH sequence from a strain affiliated with Rhizobium rosettiformans. In addition, nifH transcripts of this phylotype were also detected in spruce roots sampled in Germany, where they made up 91% of nifH transcripts detected. In contrast, in control soil or shoot samples two distinct nifH transcript sequences distantly related to nifH from Sulfurospirillum multivorans or Bradyrhizobium elkanii, respectively, were predominant. These results suggest that R. rosettiformans is involved in root-associated nitrogen fixation with sugarcane and spruce, plants that do not form root-nodule symbioses.
authors.affiliation: Lab of General Microbiology, Center for Biomolecular Interactions Bremen (CBIB), University of Bremen, D-28359 Bremen, Germany. Embrapa Agrobiologia, km 447, Estrada Antiga Rio-São Paulo, Seropédica, 23890-000, Rio de Janeiro, Brazil. Centro de Ciencias Genomicas, UNAM, Apdo. Postal No. 565-A, Cuernavaca, Mor., México.
authors.forename: Claudia Sofía
authors.initials: CS
authors.lastname: Burbano
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.forename: Kim Leonie
authors.initials: KL
authors.lastname: Rösner
authors.forename: Veronica Massena
authors.initials: VM
authors.lastname: Reis
authors.forename: Jesus
authors.initials: J
authors.lastname: Caballero-Mellado
authors.forename: Barbara
authors.initials: B
authors.lastname: Reinhold-Hurek
authors.forename: Thomas
authors.initials: T
authors.lastname: Hurek