RT Journal Article SR Electronic(1) A1 Vílchez, R A1 Pozo, C A1 Gómez, M. A A1 Rodelas, B A1 González-López, JYR 2007 T1 Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment JF Microbiology, VO 153 IS 2 SP 325 OP 337 DO https://doi.org/10.1099/mic.0.2006/002139-0 PB Microbiology Society, SN 1465-2080, AB 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., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.2006/002139-0