Silver release from decomposed hyperaccumulating Amanita solitaria fruit-body biomass strongly affects soil microbial community

Environmentally relevant concentrations of silver nanoparticles diminish soil microbial biomass but do not alter enzyme activities or microbial diversity

The increasing use of silver nanoparticles (AgNPs) due to their well-known antimicrobial activity, has led to their accumulation in soil ecosystems. However, the impact of environmental realistic concentrations of AgNPs on the soil microbial community has been scarcely studied. In this work, we have assessed the impact of AgNPs, that mimic real concentrations in nature, on tropical soils cultivated with Coffea arabica under conventional and organic management systems. We evaluated the biomass, extracellular enzyme activities, and diversity of the soil microbial community, in a microcosm experiment as a function of time. After seven days of incubation, we found an increase in microbial biomass in an AgNPs-concentration-independent manner. In contrast, after 60-day-incubation, there was a decrease in Gram+ and actinobacterial biomass, in both soils and all AgNPs concentrations. Soil physico-chemical properties and enzyme activities were not affected overall by AgNPs. Regarding the microbial community composition, only some differences in the relative abundance at phylum and genus level in the fungal community were observed. Our results suggest that environmental concentrations of AgNPs affected microbial biomass but had little impact on microbial diversity and may have little effects on the soil biogeochemical cycles mediated by extracellular enzyme activities.

Bibliometric analysis of European publications between 2001 and 2016 on concentrations of selected elements in mushrooms

This article presents a bibliometric study of 200 European publications released between 2001 and 2016, about the contamination of mushrooms by selected elements. The analysis includes figures on the type of analyte, its concentration, the species of fungi, and its country of origin. In the literature review, 492 species of mushrooms (wild-growing and cultured) found in 26 European countries and their concentration of 74 associated elements were analysed. The papers, which dealt mainly with the heavy metal (Cd, Cu, Fe, Pb, and Zn) concentrations of mushrooms, primarily came from Turkey, Poland, Spain, and the Czech Republic. More than 50% of the publications provided data about edible mushrooms. The results of the bibliometric analysis showed that over the 16 years, European research on fungal contamination by selected analytes has not lessened in popularity and is ongoing. Many of the studies underlined the need to assess the risk to human health arising from the consumption of contaminated mushrooms taken from various habitats. These results were the effect of, among other things, the strong interest in studies carried out on edible species, in which concentrations of mainly heavy metals that are dangerous to health and are marked were indicated (Cd, Pb, and Hg).

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.

Arsenic hyperaccumulation and speciation in the edible ink stain bolete (Cyanoboletus pulverulentus)

The edible ink stain bolete (Cyanoboletus pulverulentus) was found to hyperaccumulate arsenic. We analyzed 39 individual collections determined as C. pulverulentus, mostly from the Czech Republic. According to our results, concentrations of arsenic in C. pulverulentus fruit-bodies may reach 1300mgkg-1 dry weight. In most collections, data for total and bioavailable arsenic in underlying soils were collected but no significant correlation between the soil arsenic content and arsenic concentrations in the associated fruit-bodies was found. Within the fruit-bodies, we found the majority of arsenic accumulated in the hymenium. Besides occasional traces of methylarsonic acid (MA), the arsenic speciation in all mushroom samples consisted solely of dimethylarsinic acid (DMA) and no inorganic arsenic was detected. Because of the carcinogenic potential of DMA, C. pulverulentus should not be recommended as an edible mushroom and its consumption should be restricted.

Mushrooms: from nutrition to mycoremediation

Mushrooms are well known as important food items. The uses of mushrooms in the cuisine are manifolds and are being utilized for thousands of years in both Oriental and Occidental cultures. Medicinal properties of mushrooms show an immense potential as drugs for the treatment of various diseases as they are rich in a great variety of phytochemicals. In this review, we attempted to encompass the recent knowledge and scientific advancement about mushrooms and their utilization as food or curative properties, along with their natural ability to accumulate (heavy) metals/radionuclides, which leads to an important aspect of bioremediation. However, accumulation of heavy metals and radionuclides from natural or anthropogenic sources also involves potential nutritional hazards upon consumption. These hazards have been pointed out in this review incorporating a selection of the most recently published literature.

Bioaccumulation of heavy metals, metalloids, and chlorine in ectomycorrhizae from smelter-polluted area

Ectomycorrhizal (ECM) fungi contribute to the survival of host trees on metal-rich soils by reducing the transfer of toxic metals into roots. However, little is known about the ability of ECM fungi to accumulate elements in ectomycorrhizae (ECMs). Here we report Ag, As, Cd, Cl, Cu, Sb, V, and Zn contents in wild-grown Norway spruce ECMs collected in a smelter-polluted area at Lhota near Příbram, Czech Republic. The ECMs data were compared with the element concentrations determined in the corresponding non-mycorrhizal fine roots, soils, and soil extracts. Bioaccumulation factors were calculated to differentiate the element accumulation ability of ECMs inhabited by different mycobionts, which were identified by ITS rDNA sequencing. Among the target elements, the highest contents were observed for Ag, Cl, Cd, and Zn; Imleria badia ECMs showed the highest capability to accumulate these elements. ECMs of Amanita muscaria, but not of other species, accumulated V. The analysis of the proportions of I. badia and A. muscaria mycelia in ECMs by using species-specific quantitative real-time PCR revealed variable extent of the colonization of roots, with median values close to 5% (w/w). Calculated Ag, Cd, Zn and Cl concentrations in the mycelium of I. badia ECMs were 1 680, 1 510, 2 670, and 37,100 mg kg^-1 dry weight, respectively, indicating substantial element accumulation capacity of hyphae of this species in ECMs. Our data strengthen the idea of an active role of ECM fungi in soil-fungal-plant interactions in polluted environments.

On the possible role of macrofungi in the biogeochemical fate of uranium in polluted forest soils

Interactions of macrofungi with U, Th, Pb and Ag were investigated in the former ore mining district of Příbram, Czech Republic. Samples of saprotrophic (34 samples, 24 species) and ectomycorrhizal (38 samples, 26 species) macrofungi were collected from a U-polluted Norway spruce plantation and tailings and analyzed for metal content. In contrast to Ag, which was highly accumulated in fruit-bodies, concentrations of U generally did not exceed 3mg/kg which indicates a very low uptake rate and efficient exclusion of U from macrofungi. In ectomycorrhizal tips (mostly determined to species level by DNA sequencing), U contents were practically identical with those of the non-mycorrhizal fine spruce roots. These findings suggest a very limited role of macrofungi in uptake and biotransformation of U in polluted forest soils. Furthermore, accumulation of U, Th, Pb and Ag in macrofungal fruit-bodies apparently does not depend on total content and chemical fractionation of these metals in soils (tested by the BCR sequential extraction in this study).

Macro and trace mineral constituents and radionuclides in mushrooms: health benefits and risks

This article reviews and updates data on macro and trace elements and radionuclides in edible wild-grown and cultivated mushrooms. A huge biodiversity of mushrooms and spread of certain species over different continents makes the study on their multi-element constituents highly challenging. A few edible mushrooms are widely cultivated and efforts are on to employ them (largely Agaricus spp., Pleurotus spp., and Lentinula edodes) in the production of selenium-enriched food (mushrooms) or nutraceuticals (by using mycelia) and less on species used by traditional medicine, e.g., Ganoderma lucidum. There are also attempts to enrich mushrooms with other elements than Se and a good example is enrichment with lithium. Since minerals of nutritional value are common constituents of mushrooms collected from natural habitats, the problem is however their co-occurrence with some hazardous elements including Cd, Pb, Hg, Ag, As, and radionuclides. Discussed is also the problem of erroneous data on mineral compounds determined in mushrooms.

Macro and trace mineral constituents and radionuclides in mushrooms: health benefits and risks

This article reviews and updates data on macro and trace elements and radionuclides in edible wild-grown and cultivated mushrooms. A huge biodiversity of mushrooms and spread of certain species over different continents makes the study on their multi-element constituents highly challenging. A few edible mushrooms are widely cultivated and efforts are on to employ them (largely Agaricus spp., Pleurotus spp., and Lentinula edodes) in the production of selenium-enriched food (mushrooms) or nutraceuticals (by using mycelia) and less on species used by traditional medicine, e.g., Ganoderma lucidum. There are also attempts to enrich mushrooms with other elements than Se and a good example is enrichment with lithium. Since minerals of nutritional value are common constituents of mushrooms collected from natural habitats, the problem is however their co-occurrence with some hazardous elements including Cd, Pb, Hg, Ag, As, and radionuclides. Discussed is also the problem of erroneous data on mineral compounds determined in mushrooms.