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Decomposition of plant litter by the soil microbial community is an important process of controlling nutrient cycling and soil humus formation. Fungal laccases are key players in litter-associated polyphenol degradation, but little is known about the diversity and spatial distribution of fungal species with laccase genes in soils. Diversity of basidiomycete laccase genes was assessed in a cambisolic forest soil, and the spatial distribution of the sequences was mapped in a 100-m(2) plot by using polymerase chain reaction (PCR) on soil DNA extracts. Diversity of laccase sequences was higher in the organic horizon and decreased with the depth. A total of 167 different sequences sharing 44-96% oligonucleotide similarity was found in 13 soil cores harvested in the 100-m(2) plot. Dissimilarity in laccase sequence content was 67% between adjacent cores; 45.5%, 35.5% and 19% of laccase sequences were attributed to ectomycorrhizal, unknown and saprotrophic basidiomycetes, respectively. Most dominant sequences were attributed to the extramatrical hyphae of known ectomycorrhizal taxa (e.g., Russulaceae) and restricted to small patches (<0.77 m(2)) in a specific soil horizon. Soil fungi with laccase genes occupied different niches and showed strikingly variable distribution patterns. The distribution of laccase sequences, and corresponding fungi, likely reflected a part of the oxidative potential in soils.

The ability of soil-living oribatid mites to disperse fungal propagules on their bodies was investigated. Classical plating methods were applied to cultivate these fungi and to study their morphology. Molecular markers were used for further determination. The nuclear ribosomal large subunit and the nuclear ribosomal internal transcribed spacer of DNA extracts of the cultured fungi as well as total DNA extracts of the mites themselves, also containing fungal DNA, were amplified and sequenced. Based on phylogenetic analysis, a total of 31 fungal species from major fungal groups were found to be associated with oribatid mites, indicating that mites do not selectively disperse specific species or species groups. The detected taxa were mainly saprobiontic, cosmopolitan (e.g., Alternaria tenuissima), but also parasitic fungi (Beauveria bassiana) for whose dispersal oribatid mites might play an important role. In contrast, no mycorrhizal fungi were detected in association with oribatid mites, indicating that their propagules are dispersed in a different way. In addition, fungi that are known to be a preferred food for oribatid mites such as the Dematiacea were not detected in high numbers. Results of this study point to the potential of oribatid mites to disperse fungal taxa in soil and indicate that co-evolutionary patterns between oribatid mites and their associated fungi might be rare or even missing in most cases, since we only detected ubiquitous taxa attached to the mites.

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