Avis d'expert en biologie environnementale

Effects of Gadolinium and Tin to the Production of Oxidative Enzymes and the Growth of Five Basidiomycetous Fungi

Mika A Kähkönen, Otto Miettinen, Anu Kinnunen and Annele Hatakka

Effects of Gadolinium and Tin to the Production of Oxidative Enzymes and the Growth of Five Basidiomycetous Fungi

Effects of gadolinium (Gd) and tin (Sn) on the growth and production of oxidative enzymes with five basidiomycetous fungi were tested. For this study we have selected well-known white-rot fungi Obba rivulosa and Kuehneromyces mutabilis, in addition to this we have tested three new isolates, the white-rot fungus Phlebia subochracea, the litter-degrading fungus Gymnopus dryophilus and the brown-rot fungus Heliocybe sulcata. This approach allowed us to find possible new sources for oxidative enzymes, such as laccases and versatile peroxidases (VPs). All five tested fungi grew in the presence of Gd (0-200 mg/l) or Sn (0-200 mg/l) on ABTS (2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) containing plates. The growth rate of H. sulcata was tolerant to Gd and Sn (0- 200 mg/l). The growth rates of P. subochracea and G. dryophilus were sensitive to Gd (5-200 mg/l) and Sn (5-200 mg/l). O. rivulosa, K. mutabilis, P. subochracea and G. dryophilus formed colour zones on the ABTS plates indicating that these fungi produced oxidative enzymes, most probably laccases. The brown-rot fungus H. sulcata did not form colour zone on the ABTS plate indicating that this fungus did not produce laccase. The production of laccase with G. dryophilus and K. mutabilis was tolerant to Gd (0-200 mg/l) and Sn (0-200 mg/l). The production of laccase with P. subochracea was sensitive to Gd (5-200 mg/l) and Sn (5-200 mg/l). P. subochracea decolorized the dye Reactive Black 5 without or with Gd and Sn (0- 200 mg/l) indicating the production of VP. O. rivulosa, K. mutabilis, G. dryophilus and H. sulcata did not produce VP. The production of VP by P. subochracea was sensitive to 200 mg/l Gd and Sn.