New horizons in geomycology

Disentangling the factors of contrasting silver and copper accumulation in sporocarps of the ectomycorrhizal fungus Amanita strobiliformis from two sites

Amanita strobiliformis (European Pine Cone Lepidella) is an ectomycorrhizal fungus of the Amanitaceae family known to hyperaccumulate Ag in the sporocarps. Two populations (ecotypes) of A. strobiliformis collected from two urban forest plantations in Prague, Czech Republic, were investigated. The concentrations of Ag, Cu, Cd, and Zn were determined in the mushrooms. The metal mobility and fractionation in the soils was investigated by single extractions and sequential extraction. The soil distribution of A. strobiliformis mycelium was assessed by quantitative polymerase chain reaction (qPCR). The metal uptake from the soil into the mushroom sporocarps was traced by Pb isotopic fingerprinting. The findings suggested that A. strobiliformis (i) accumulates primarily Ag from the topsoil layer (circa 12cm deep) and (ii) accumulates Ag associated with the "reducible soil fraction". The concentrations of all metals, particularly Ag and Cu, were significantly higher in the A. strobiliformis sporocarps from one of the investigated sites (Klíčov). The elevated concentrations of Ag in the sporocarps from Klíčov can possibly be attributed to the higher Ag content in the topsoil layer found at this site. However, the simultaneously elevated concentrations of Cu in A. strobiliformis from Klíčov cannot be explained by the differences in the geochemical background and should be attributed to biological factors.

Differences in structure of northern Australian hypolithic communities according to location, rock type, and gross morphology

Hypolithic communities (under translucent rocks) were compared between a semi-arid site (Wave Hill) and a site with considerably higher rainfall (Lake Bennett) to test the hypothesis that the communities at the higher rainfall site would be more diverse. A total of 153 cyanobacteria operational taxonomic units (OTUs) were identified, and only 50 of those were found at both sites. Of these, only two were core OTUs, as defined as being present in ≥90% of samples, highlighting the extreme differences in the cyanobacterial communities at the two sites. At Wave Hill, we compared the composition of the cyanobacterial components under two different rock types (quartz and prehnite) to determine if the different minerals would result in different hypolithic communities, but no differences were found. Of the 42 core OTUs found at Wave Hill, 22 (52%) were shared between the two rock types. As hypothesised, the diversity of both cyanobacteria and eukaryotes in the hypolithic communities was significantly higher at Lake Bennett. Some hypolithic communities were thin and tightly adhered to the rock surface, but others were thicker and could be peeled off the rock in sheets. However, the two types were not significantly different in OTU composition. Metazoans, primarily nematodes, were ubiquitous, raising the possibility that nematodes may act as vectors to transport the components of hypolithic communities from rock to rock as a mechanism of colonization.

Speciation analysis of elements accumulated in Cystoderma carcharias from clean and smelter-polluted sites

Collections of Cystoderma carcharias sporocarps were sampled from clean and smelter-polluted sites and analyzed for Ag, As, Cd, Cu, Pb, Se, and Zn contents. Concentrations of all elements were significantly higher in samples from the smelter-polluted area. Except for As and Pb, all elements were effectively accumulated in the sporocarps at both clean and polluted sites. With the highest concentration of 604 mg Cd kg^-1, C. carcharias can be considered as Cd hyperaccumulator. As revealed by HPLC-ICPQQQMS analysis, the As species in sporocarps from clean and polluted areas involved besides the major arsenobetaine a variety of known and unknown arsenicals; the occurrence of dimethylarsinoylacetate and trimethylarsoniopropionate is reported for the first time for gilled fungi (Agaricales). Size-exclusion chromatography of C. carcharias extracts supported by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and RP-HPLC data indicated that detoxification of intracellular Cd and Cu may largely rely on metallothioneins (MT) or MT-like peptides, not phytochelatins.