Microbial Characterization of Mercury-Reducing Mixed Cultures Enriched with Different Carbon Sources

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  • Carvalho Gilda
    Instituto de Biologia Experimental e Tecnológica (IBET), Av. da República (EAN) REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa (UNL)
  • Almeida Bárbara
    Instituto de Biologia Experimental e Tecnológica (IBET), Av. da República (EAN) Instituto de Tecnologia Química e Biológica (ITQB), Universidade Nova de Lisboa (UNL)
  • Fradinho Joana
    REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa (UNL)
  • Oehmen Adrian
    REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa (UNL)
  • Reis Maria A.M.
    REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa (UNL)
  • Crespo M. Teresa Barreto
    Instituto de Biologia Experimental e Tecnológica (IBET), Av. da República (EAN) Instituto de Tecnologia Química e Biológica (ITQB), Universidade Nova de Lisboa (UNL)

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Abstract

The use of mixed microbial cultures enriched for biological mercury removal is explored in this paper, focusing on the ecological shifts occurring throughout acclimatization to mercury and on the long-term stability of four microbial enrichments. The 16S rRNA genetic profiles obtained by denaturing gradient gel electrophoresis (DGGE) revealed that the glucose and ethanol cultures had similar profiles, whereas the acetate cultures diverged into a totally dissimilar cluster. Quantification of the merA gene copies in each enrichment showed higher values for the glucose culture, followed by the ethanol and then the acetate cultures, which was consistent with the mercury removal performance throughout the study. Isolates were obtained from the four cultures and analyzed with respect to their genetic (16S rRNA) and functional (merA) phylogenies in order to identify mercury-resistant species enriched with different carbon sources. All mercury-resistant isolates obtained from the glucose and ethanol cultures belonged to the Gammaproteobacteria, whereas acetate cultures also contained members of other phyla, with differences in merA sequences. Higher phylogenetic than functional diversity of the isolates, together with increasing merA copies even after culture stabilisation, highlight the role of horizontal gene transfer in the acclimatization process.<br>

Journal

  • Microbes and Environments

    Microbes and Environments 26 (4), 293-300, 2011

    Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

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