Activity and production of extracellular enzymes by saprotrophic litter-decomposing basidiomycetes Hypholoma fasciculare and Rhodocollybia butyracea was studied in microcosms with reconstructed L, O and Ah horizons of a soil profile of Quercus petraea forest soil. Both H.fasciculare and R. butyracea colonized the L layer of microcosms rapidly, while the colonization of 0 layer was slower. The Ah layer was substantially colonized only by R. butyracea. Enzyme activities in the soil microcosms decreased from the L layer > O layer > Ah layer and activities in microcosms inoculated with the fungi were quite similar to each other. Compared to control, the most apparent was the increase of ligninolytic enzyme activities. Laccase activities in H.fasciculare and R. butyracea-colonized L layers were 3-fold compared to control and the activity maxima of Mn-peroxidase in fungus-colonized O layers were 2-3-fold and in the L layers up to 40-fold compared to controls. Activities of cellulolytic enzymes, chitinase and acidic phosphatase in both fungal treatments were higher in the L layer on weeks 2-6 while the activity of alkaline phosphatase did not show differences between fungus-colonized and control treatments. Both fungi decreased fungal CFU in the L layer but significantly increased the counts in the O layer. Both fungi also increased bacterial CFU in the O layer, R. butyracea more than H. fasciculare. The analysis of fungal and bacterial biomass based on ergosterol content and PLFA analysis showed a sharp decrease from L to Ah layer, but did not show significant differences among treatments. (C) 2007 Elsevier Inc. All rights reserved.