Abstract
Although many fungi are known to be able to perform bioweathering of rocks and minerals, little information is available concerning the role of basidiomycetes in this process. The wood-rotting basidiomycete Schizophyllum commune was investigated for its ability to degrade black slate, a rock rich in organic carbon. Mechanical pressure of hyphae and extracellular polymeric substances was investigated for biophysical weathering. A mixed ß1-3/ß1-6 glucan, likely schizophyllan that is well known from S. commune, could be identified on black slate surfaces. Secretion of siderophores and organic acids as biochemical weathering agents was shown. Both may contribute to biochemical weathering in addition to enzymatic functions. Previously, the exoenzyme laccase was believed to attack organic the matter within the black slate, thereby releasing metals from the rock. Here, overexpression of laccase showed enhanced dissolution of quartz phases by etching and pitting. At the same time, the formation of a new secondary mineral phase, whewellite, could be demonstrated. Hence, a more comprehensive understanding of biophysical as well as biochemical weathering by S. commune could be reached and unexpected mechanisms like quartz dissolution linked to shale degradation.
Highlights
Black slates are sedimentary low-grade metamorphic rocks that contain more than 0.5 wt.% organic carbon (Fischer et al, 2007)
The wood-rotting basidiomycete Schizophyllum commune was investigated for its ability to degrade black slate, a rock rich in organic carbon
Mechanical pressure of hyphae and extracellular polymeric substances was investigated for biophysical weathering
Summary
Black slates are sedimentary low-grade metamorphic rocks that contain more than 0.5 wt.% organic carbon (Fischer et al, 2007). Due to the formation conditions of this sedimentary rock material, it contains high amounts of organic matter, metals and minerals like pyrite (Fischer et al, 2007; Marynowski et al, 2011). Black slate undergoes weathering processes that result in the degradation of organic matter and the release of organic chemical compounds (Fischer et al, 2007). Such oxidative weathering of black slate contributes to the global cycling of carbon (Berner, 2003; Petsch et al, 2005). Mining activity and the resulting mining waste heaps increase the exposure of huge amounts of rock material to atmospheric oxygen, which causes further degradation of organic matter and the oxidation of pyrite (Lottermoser, 2003)
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