Arsenic hyperaccumulation in macrofungi

Fungi are indispensable constituents of our environment. They play an important role in the biogeochemical cycling and transformation of chemical elements in ecosystems. For example, some studies reported fungal species accumulating unusually high amounts of arsenic. Surprisingly, not much is known about this phenomenon until now, and the biological importance for this process is also not clear. In our project we will collect many species of mushrooms in the Czech Republic and Austria. By analyzing the arsenic concentrations in these samples we will be able to complement the existing list of arsenic accumulating fungi. Further on, we will compare the arsenic levels of fungi from arsenic contaminated areas with samples from clean sites. A special task will be the identification of the different arsenic compounds that are occurring in the samples. With these results we will gain more insight into the biotransformation of the element in nature, especially in fungi. Also possible connections of arsenic to other elements like zinc can help elucidating this question. Hence, these correlations will be investigated as well. Beside the analysis of collected fungi, we will grow some fungi in vitro and compare the arsenic speciation with wild types. For the determination of arsenic in the samples we will use inductively coupled plasma mass spectrometry and neutron activation analysis. The separation of different compounds and proteins will be carried out with high performance liquid chromatography, electrophoresis and others. We will identify unknown compounds with high resolution mass spectrometry. In the different experiments, we will also use other analytical and biochemical methods to achieve our goals. The project is remarkable and unique, especially because of the close collaboration of researchers from different disciplines, namely analytical chemistry, biochemistry, geochemistry, and mycology. The multidisciplinary approach will enable us to achieve valuable complex data. With our results it will be possible to better understand the phenomenon of arsenic hyper-accumulation in fungi. Substantial new insights will contribute to the knowledge on the behavior of arsenic in the environment.

Arsenic hyperaccumulation in macrofungi Fungi are essential constituents of our environment and play an important role in the distribution and transformation of chemical elements in nature. For example, many plants form a mycorrhiza (community) with fungi, of which both partners are profiting. While the fungus delivers mineral nutrients to the plant, it obtains sugar as energy source in return. It has been shown that several fungal species can accumulate different elements. Some of these fungi have specialized on arsenic and are taking up extremely high amounts of this element. Various aspects of this phenomenon have now been studied in this international, interdisciplinary project by analytical chemists, mycologists (mushroom experts) and biochemists from Austria and the Czech Republic. Some fungal species could be identified as so-called arsenic (hyper)accumulators. Examples are deer truffles (Elaphomyces spp.), which are sought by wild boars, and the edible mushroom Cyanoboletus pulverulentus (ink stain bolete). In the latter one, up to more than 1000 mg As/kg (in the dried mushroom) have been detected. Apart from the high arsenic concentrations, also the chemical compounds of arsenic (the arsenic speciation) in the mushrooms are exceptional. While there are only a few arsenic compounds present in animals and plants, up to 20 water soluble arsenic compounds could be found in the investigated mushroom samples. The fungal species is the main determining factor for the mushroom's arsenic speciation; there are some fungi that only contain inorganic (toxic) arsenic, and others that mainly contain the harmless arsenobetaine, which is otherwise only present in marine organisms. There are also fungi where dimethylarsinic acid or methylarsonic acid are found, which are also occurring in animals and plants. Some other mushrooms contain a mixture of many different arsenicals. The arsenic speciation is usually the same in all fruit-bodies of one fungal species, and is hardly influenced by other factors like the soil. Further, a new natural arsenic compound (homoarsenocholine) was identified in coral mushrooms (Ramaria spp.) during the project. With state-of-the-art methods, 35 additional elements were determined in more than 1000 mushroom samples. This led, for example, to the discovery that Cystoderma Carcharias and Thelephora penicillata take up extremely high concentrations of cadmium and other heavy metals from polluted soils. It can be derived from the results that the element profile and the arsenic speciation can be used as additional information to identify mushrooms. Moreover, the knowledge of arsenic species in mushrooms was significantly expanded, which will be of enormous help to better understand the arsenic metabolism in fungi and the role of this element in the community with plants. Last but not least, good news for mushroom lovers: Typically consumed mushrooms (Cantharelle, porcini and parasol) are not accumulating arsenic.