Extracellular laccase activity and transcript levels of putative laccase genes during removal of  the xenoestrogen technical nonylphenol by the aquatic hyphomycete Clavariopsis aquatica

Authors


  • Editor: Geoffrey Gadd

  • Present addresses: Harald Kellner, School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA.
    François Buscot, Department of Soil Ecology, UFZ – Helmholtz Centre for Environmental Research, 06120 Halle, Saale, Germany.

Correspondence: Magali Solé, Department of Environmental Microbiology, UFZ – Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany. Tel.: +49 341 235 1364; fax: +49 341 235 2247; e-mail: magali.sole@ufz.de

Abstract

We investigated the influence of potential laccase inducers with environmental relevance on extracellular laccase activity and removal of the xenoestrogen technical nonylphenol (tNP) by the aquatic hyphomycete Clavariopsis aquatica. Concomitantly, we identified two putative laccase gene fragments (lcc1 and lcc2) and have followed their expression during removal of tNP under different conditions. Our results indicate a significant effect of copper on extracellular laccase activity in supernatants of fungal cultures. Laccase activity was highest in the presence of copper when added together with vanillic acid, followed by copper when used alone. Only slight laccase activities were recorded in the presence of only vanillic acid, whereas in the absence of either compound laccase activities were negligible. Laccase activity was well correlated with the removal efficiency of tNP, indicating the involvement of laccase in tNP bioconversion. Overall, lcc2 was less expressed than lcc1. The expression of lcc1 and lcc2 correlated only partially with the measured laccase activity, suggesting the existence of cell-associated laccase fractions not detectable in fungal culture supernatants and/or the existence of additional laccase genes.

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