title: Abundance and genetic diversity of nifH gene sequences in anthropogenically affected Brazilian mangrove sediments.
abstract: Although mangroves represent ecosystems of global importance, the genetic diversity and abundance of functional genes that are key to their functioning scarcely have been explored. Here, we present a survey based on the nifH gene across transects of sediments of two mangrove systems located along the coast line of São Paulo state (Brazil) which differed by degree of disturbance, i.e., an oil-spill-affected and an unaffected mangrove. The diazotrophic communities were assessed by denaturing gradient gel electrophoresis (DGGE), quantitative PCR (qPCR), and clone libraries. The nifH gene abundance was similar across the two mangrove sediment systems, as evidenced by qPCR. However, the nifH-based PCR-DGGE profiles revealed clear differences between the mangroves. Moreover, shifts in the nifH gene diversities were noted along the land-sea transect within the previously oiled mangrove. The nifH gene diversity depicted the presence of nitrogen-fixing bacteria affiliated with a wide range of taxa, encompassing members of the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and also a group of anaerobic sulfate-reducing bacteria. We also detected a unique mangrove-specific cluster of sequences denoted Mgv-nifH. Our results indicate that nitrogen-fixing bacterial guilds can be partially endemic to mangroves, and these communities are modulated by oil contamination, which has important implications for conservation strategies.
authors.affiliation: Center for Nuclear Energy in Agriculture, University of São Paulo, CENA/USP, Piracicaba, Brazil.
authors.forename: Armando Cavalcante Franco
authors.initials: AC
authors.lastname: Dias
authors.forename: Michele de Cassia
authors.initials: Mde C
authors.lastname: Pereira e Silva
authors.forename: Simone Raposo
authors.initials: SR
authors.lastname: Cotta
authors.forename: Francisco
authors.initials: F
authors.lastname: Dini-Andreote
authors.forename: Fábio Lino
authors.initials: FL
authors.lastname: Soares
authors.forename: Joana Falcão
authors.initials: JF
authors.lastname: Salles
authors.forename: João Lúcio
authors.initials: JL
authors.lastname: Azevedo
authors.forename: Jan Dirk
authors.initials: JD
authors.lastname: van Elsas
authors.forename: Fernando Dini
authors.initials: FD
authors.lastname: Andreote
mesh_terms: D032407:Avicennia / Q000382:microbiology*; D001419:Bacteria / Q000145:classification* / Q000235:genetics; D058448:Biota; D001938:Brazil; D029764:Combretaceae / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D043982:Rhizophoraceae / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D010088:Oxidoreductases; C029130:nitrogenase reductase