Replicability of dominant bacterial populations after long-term surfactant-enrichment in lab-scale activated sludge

Authors

  • Mariana Lozada,

    1. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI-CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Vuelta de Obligado 2490 (1428), Buenos Aires, Argentina.
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    • These authors contributed equally to this work.

  • Eva L. M. Figuerola,

    1. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI-CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Vuelta de Obligado 2490 (1428), Buenos Aires, Argentina.
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    • These authors contributed equally to this work.

  • Raúl F. Itria,

    1. Instituto Nacional de Tecnología Industrial (INTI-Ingeniería Ambiental) Paseo Colón 850 (1063), Buenos Aires, Argentina.
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  • Leonardo Erijman

    Corresponding author
    1. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI-CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Vuelta de Obligado 2490 (1428), Buenos Aires, Argentina.
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*E-mail erijman@dna.uba.ar; Tel. (+54) 11 4783 2871; Fax (+54) 11 4786 8578.

Summary

Bacterial communities were examined in replicate lab-scale activated sludge reactors after a period of several months of enrichment with non-ionic nonylphenol ethoxylate (NPE) surfactants. Four sequential batch reactors were fed with synthetic sewage, two of which received additionally NPE. Small subunit rDNA-derived denaturing gel gradient electrophoresis (DGGE) profiles and 16S rDNA clone libraries were dominated by clones of Gammaproteobacteria class. Sequences of the other codominant rDNA phylotypes observed only in DGGE from NPE-amended reactors were, respectively, associated with the Group III of the Acidobacteria phylum. Intriguingly, 16S rRNA content from abundant Gammaproteobacteria cells was unexpectedly low. In addition to Acidobacteria, rRNA-derived DGGE profiles were dominated by members of the order Burkholderiales (of the Betaproteobacteria) and of the genus Sphingomonas (a member of the Alphaproteobacteria). Specific oligonucleotide probes for the selected ribotypes were designed and applied for quantitative real time polymerase chain reaction and fluorescence in situ hybridization, confirming their dominance in treated reactors. The parallel abundance of unique phylotypes in replicate reactors implies a distinctive selection of dominant organisms, which are better adapted to specialized niches in the highly selective environment.

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