title: Sulfate-reducing bacteria in floating macrophyte rhizospheres from an Amazonian floodplain lake in Bolivia and their association with Hg methylation.
abstract: Five subgroups of sulfate-reducing bacteria (SRB) were detected by PCR in three macrophyte rhizospheres (Polygonum densiflorum, Hymenachne donacifolia, and Ludwigia helminthorriza) and three subgroups in Eichhornia crassipes from La Granja, a floodplain lake from the upper Madeira basin. The SRB community varied according to the macrophyte species but with different degrees of association with their roots. The rhizosphere of the C4 plant Polygonum densiflorum had higher frequencies of SRB subgroups as well as higher mercury methylation potentials (27.5 to 36.1%) and carbon (16.06 +/- 5.40%), nitrogen (2.03 +/- 0.64%), Hg (94.50 +/- 6.86 ng Hg g(-1)), and methylmercury (8.25 +/- 1.45 ng Hg g(-1)) contents than the rhizosphere of the C3 plant Eichhornia crassipes. Mercury methylation in Polygonum densiflorum and Eichhornia crassipes was reduced when SRB metabolism was inhibited by sodium molybdate.
authors.affiliation: Instituto de Biología Molecular y Biotecnología, Facultad de Ciencias Puras, Universidad Mayor de San Andrés, La Paz, Bolivia. darioacha@yahoo.ca
authors.forename: Darío
authors.initials: D
authors.lastname: Achá
authors.forename: Volga
authors.initials: V
authors.lastname: Iñiguez
authors.forename: Marc
authors.initials: M
authors.lastname: Roulet
authors.forename: Jean Remy Davée
authors.initials: JR
authors.lastname: Guimarães
authors.forename: Ruddy
authors.initials: R
authors.lastname: Luna
authors.forename: Lucia
authors.initials: L
authors.lastname: Alanoca
authors.forename: Samanta
authors.initials: S
authors.lastname: Sanchez
mesh_terms: D001838:Bolivia; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D008628:Mercury / Q000378:metabolism; D008745:Methylation; D008767:Methylmercury Compounds / Q000378:metabolism*; D029594:Onagraceae / Q000382:microbiology* / Q000502:physiology; D018517:Plant Roots / Q000382:microbiology* / Q000502:physiology; D006109:Poaceae / Q000382:microbiology* / Q000502:physiology; D028502:Polygonum / Q000382:microbiology* / Q000502:physiology; D016999:Sulfur-Reducing Bacteria / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury