title: Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment.
abstract: The structure, biological activity and microbial biodiversity of a biofilm used for the removal of copper from groundwater were studied and compared with those of a biofilm grown under copper-free conditions. A laboratory-scale submerged fixed biofilter was fed with groundwater (2.3 l h(-1)) artificially polluted with Cu(II) (15 mg l(-1)) and amended with sucrose (150 mg l(-1)) as carbon source. Between 73 and 90 % of the Cu(II) was removed from water during long-term operation (over 200 days). The biofilm was a complex ecosystem, consisting of eukaryotic and prokaryotic micro-organisms. Scanning electron microscopy revealed marked structural changes in the biofilm induced by Cu(II), compared to the biofilm grown in absence of the heavy metal. Analysis of cell-bound extracellular polymeric substances (EPS) demonstrated a significant modification of the composition of cell envelopes in response to Cu(II). Transmission electron microscopy and energy-dispersive X-ray microanalysis (EDX) showed that copper bioaccumulated in the EPS matrix by becoming bound to phosphates and/or silicates, whereas copper accumulated only intracytoplasmically in cells of eukaryotic microbes. Cu(II) also decreased sucrose consumption, ATP content and alkaline phosphatase activity of the biofilm. A detailed study of the bacterial community composition was conducted by 16S rRNA-based temperature gradient gel electrophoresis (TGGE) profiling, which showed spatial and temporal stability of the species diversity of copper-exposed biofilms during biofilter operation. PCR reamplification and sequencing of 14 TGGE bands showed the prevalence of alphaproteobacteria, with most sequences (78 %) affiliated to the Sphingomonadaceae. The major cultivable colony type in plate counts of the copper-exposed biofilm was also identified as that of Sphingomonas sp. These data confirm a major role of these organisms in the composition of the Cu(II)-removing community.
authors.affiliation: Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Instituto del Agua, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Vílchez
authors.affiliation: Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Instituto del Agua, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Pozo
authors.affiliation: Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Departamento de Ingeniería Civil, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.|Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Instituto del Agua, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Gómez
authors.affiliation: Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Departamento de Microbiología, Facultad de Farmacia, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.|Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Instituto del Agua, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Rodelas
authors.affiliation: Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Departamento de Microbiología, Facultad de Farmacia, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.|Grupo de Microbiología Ambiental (Environmental Microbiology Research Group), Instituto del Agua, Escuela Superior de Ingenieros de Caminos, Canales y Puertos, Universidad de Granada, 18071 Granada, Spain.
authors.forename: J
authors.initials: J
authors.lastname: González-López
mesh_terms: D001673:Biodegradation, Environmental; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D003300:Copper / Q000378:metabolism / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D004586:Electrophoresis / Q000379:methods; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D020578:Sphingomonas / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000494:pharmacology; D018508:Water Purification / Q000379:methods
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D003300:Copper