title: nifH pyrosequencing reveals the potential for location-specific soil chemistry to influence N2 -fixing community dynamics.
abstract: A dataset of 87 020 nifH reads and 16 782 unique nifH protein sequences obtained over 2 years from four locations across a gradient of agricultural soil types in Argentina were analysed to provide a detailed and comprehensive picture of the diversity, abundance and responses of the N2 -fixing community in relation to differences in soil chemistry and agricultural practices. Phylogenetic analysis revealed an expected high proportion of Alphaproteobacteria, Betaproteobacteria and Deltaproteobacteria, mainly relatives to Bradyrhizobium and Methylosinus/Methylocystis, but a surprising paucity of Gammaproteobacteria. Analysis of variance and stepwise regression modelling suggested location and treatment-specific influences of soil type on diazotrophic community composition and organic carbon concentrations on nifH diversity. nifH gene abundance, determined by quantitative real-time polymerase chain reaction, was higher in agricultural soils than in non-agricultural soils, and was influenced by soil chemistry under intensive crop rotation but not under monoculture. At some locations, sustainable increased crop yields might be possible through the management of soil chemistry to improve the abundance and diversity of N2 -fixing bacteria.
authors.affiliation: Instituto de Botánica del Nordeste (IBONE), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste-CONICET, Corrientes, Argentina; Instituto de Biotecnología y Biología Molecular (IBBM), Universidad Nacional de La Plata-CONICET, La Plata, Argentina.
authors.forename: Mónica M
authors.initials: MM
authors.lastname: Collavino
authors.forename: H James
authors.initials: HJ
authors.lastname: Tripp
authors.forename: Ildiko E
authors.initials: IE
authors.lastname: Frank
authors.forename: María L
authors.initials: ML
authors.lastname: Vidoz
authors.forename: Priscila A
authors.initials: PA
authors.lastname: Calderoli
authors.forename: Mariano
authors.initials: M
authors.lastname: Donato
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Zehr
authors.forename: O Mario
authors.initials: OM
authors.lastname: Aguilar
mesh_terms: D000383:Agriculture; D001118:Argentina; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D009586:Nitrogen Fixation / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics*; D010802:Phylogeny; D020560:Proteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D012987:Soil; D010088:Oxidoreductases; C029130:nitrogenase reductase