Death caps (Amanita phalloides) frequently establish from sexual spores, but individuals can grow large and live for more than a decade in invaded forests

Global change is reshaping Earth's biodiversity, but the changing distributions of nonpathogenic fungi remain largely undocumented, as do mechanisms enabling invasions. The ectomycorrhizal Amanita phalloides is native to Europe and invasive in North America. Using population genetics and genomics, we sought to describe the life history traits of this successfully invading symbiotic fungus. To test whether death caps spread underground using hyphae, or aboveground using sexual spores, we mapped and genotyped mushrooms from European and US sites. Larger genetic individuals (genets) would suggest spread mediated by vegetative growth, while many small genets would suggest dispersal mediated by spores. To test whether genets are ephemeral or persistent, we also sampled from populations over time. At nearly every site and across all time points, mushrooms resolve into small genets. Individuals frequently establish from sexual spores. But at one Californian site, a single individual measuring nearly 10 m across dominated. At two Californian sites, the same genetic individuals were discovered in 2004, 2014, and 2015, suggesting single individuals (both large and small) can reproduce repeatedly over relatively long timescales. A flexible life history strategy combining both mycelial growth and spore dispersal appears to underpin the invasion of this deadly perennial ectomycorrhizal fungus.

Diversity, Dispersal and Mode of Reproduction of Amanita exitialis in Southern China

Amanita exitialis is a poisonous mushroom and has caused many deaths in southern China. In this study, we collected 118 fruiting bodies of A. exitialis from seven different sites in Guangdong Province in southern China and investigated their genetic relationships using 14 polymorphic molecular markers. These 14 markers grouped the 118 fruiting bodies into 20 multilocus genotypes. Among these 20 genotypes, eight were each found only once while the remaining 12 were each represented by two to 54 fruiting bodies. Interestingly, among the 12 shared genotypes, four were shared between/among local populations that were separated by as far as over 80 km, a result consistent with secondary homothallic reproduction and long-distance spore dispersal. Despite the observed gene flow, significant genetic differentiations were found among the local populations, primarily due to the over-representation of certain genotypes within individual local populations. STRUCTURE analyses revealed that the 118 fruiting bodies belonged to three genetic clusters, consistent with divergence within this species in this geographic region. Interestingly, we found an excess of heterozygous individuals at both the local and the total sample level, suggesting potential inbreeding depression and heterozygous advantage in these populations of A. exitialis. We discuss the implications of our results for understanding the life cycle, dispersal, and evolution of this poisonous mushroom.

Microanalysis characterization of bioactive protein-bound polysaccharides produced by Amanita ponderosa cultures

Different compounds of edible mushrooms are responsible for their bioactivity. The ability to synthesize polysaccharides, namely protein-polysaccharide (PPS) complexes, is related to the antioxidant capacity of these compounds and present great interest in preventing a number of diseases, including cancer, cardiovascular and auto-immune diseases, and accelerated aging. Amanita ponderosa are wild edible mushrooms that grow in Mediterranean "montado" areas [Portuguese name given to cork oak (Quercus suber) and holm oak (Quercus ilex) forests]. The aim of this study was to evaluate the production of PPS complexes obtained from A. ponderosa cultures using a new microanalytical approach to quickly and easily monitor the production process. Microanalysis using Fourier-transform infrared using attenuated total reflection and Raman spectroscopy of PPS samples showed spectra compatible with identification of this type of compound in culture extracts. PPS separated by size-exclusion chromatography showed seven main complexes. Molecular weights of the main PPS complexes isolated from cultures ranged between 1.5 and 20 kDa and did not present toxicity against Artemia salina, demonstrating the potential of A. ponderosa as a source of biologically active compounds with nutraceutical value. Application of this microanalytical approach to monitoring the production of PPS compounds can be successfully applied in biotechnological processes.

The irreversible loss of a decomposition pathway marks the single origin of an ectomycorrhizal symbiosis

Microbial symbioses have evolved repeatedly across the tree of life, but the genetic changes underlying transitions to symbiosis are largely unknown, especially for eukaryotic microbial symbionts. We used the genus Amanita, an iconic group of mushroom-forming fungi engaged in ectomycorrhizal symbioses with plants, to identify both the origins and potential genetic changes maintaining the stability of this mutualism. A multi-gene phylogeny reveals one origin of the symbiosis within Amanita, with a single transition from saprotrophic decomposition of dead organic matter to biotrophic dependence on host plants for carbon. Associated with this transition are the losses of two cellulase genes, each of which plays a critical role in extracellular decomposition of organic matter. However a third gene, which acts at later stages in cellulose decomposition, is retained by many, but not all, ectomycorrhizal species. Experiments confirm that symbiotic Amanita species have lost the ability to grow on complex organic matter and have therefore lost the capacity to live in forest soils without carbon supplied by a host plant. Irreversible losses of decomposition pathways are likely to play key roles in the evolutionary stability of these ubiquitous mutualisms.

Characterisation of ectomycorrhizal formation by the exotic fungus Amanita muscaria with Nothofagus cunninghamii in Victoria, Australia

The occurrence of the exotic ectomycorrhizal fungus Amanita muscaria in a mixed Nothofagus-Eucalyptus native forest was investigated to determine if A. muscaria has switched hosts to form a successful association with a native tree species in a natural environment. A mycorrhizal morphotype consistently found beneath A. muscaria sporocarps was examined, and a range of morphological and anatomical characteristics in common with those described for ectomycorrhizae formed by A. muscaria on a broad range of hosts were observed. A full description is provided. The likely plant associate was determined to be Nothofagus cunninghamii based upon anatomy of the roots. Analysis of ITS-1 and ITS-2 regions of nuclear ribosomal DNA sequences confirmed the identities of both fungal and plant associates. These findings represent conclusive evidence of the invasion of a non-indigenous ectomycorrhizal fungus into native forest and highlight the ecological implications of this discovery.

Mercury in European Blushers, Amanita rubescens, mushrooms and topsoils: bioconcentration potential and intake assessment

Total mercury content has been determined in fruiting bodies of European Blushers and topsoils collected from 11 sites across Poland in 2006-2008. Mercury analysis was carried out using a validated analytical method and cold-vapour atomic absorption (CV-AAS). The European Blusher effectively accumulated mercury in fruiting bodies. The mean values of total mercury in caps of European Blushers from background (uncontaminated) areas were from 0.22 to 1.0 (0.067-3.2) and in stipes from 0.16 to 0.65 (0.071-2.7) μg/g dry weight. In topsoil beneath to fruiting bodies, the median Hg concentration at 10 sites in Northern Poland varied between 0.030 and 0.072 (0.0096-0.19) μg/g dw, and in one site in Southern Poland was 0.20 (0.079-0.34) μg/g dw. Data on Hg in European Blushers from different countries were reviewed. The mean concentrations of total Hg in caps of European Blushers from two "pristine" sites in northern part of Poland were ∼1.0 μg/g dw. A meal made with 300-500 g of fresh caps of European Blushers collected at such sites (assuming 90% water content in caps) can result in Hg intake of 0.0003-0.0005 mg Hg/kg bm (assuming a 60 kg bm), which is a dose equipotent to a new provisional tolerable weekly intake (PTWI) value set for inorganic Hg.

Distribution and abundance of the introduced ectomycorrhizal fungus Amanita phalloides in North America

Despite a growing awareness of the global reach of ectomycorrhizal (EM) fungal introductions, little is known about the fate of introduced EM fungi in novel ranges. Using herbarium specimens, species distribution models, and field collections of sporocarps, root tips and extramatrical mycelia, we assessed the distribution and abundance of the European species Amanita phalloides in North America. There are two distinct ranges of the fungus, one along the West Coast (California to British Columbia) and the second on the East Coast (Maryland to Maine). As predicted by a species distribution model, the West Coast range is larger. Amanita phalloides is more frequently found in native forests on the West Coast than on the East Coast. At Point Reyes Peninsula in California, A. phalloides dominates community sporocarp biomass, and is frequent as root tips. In individual soil cores at Point Reyes, root tips of A. phalloides make up 50% of total root tip biomass. Hyphae of A. phalloides are frequent, but make up only 2% of total hyphal biomass. The contrasting patterns of the distribution and abundance of A. phalloides on the East and West Coasts of North America may influence both its future spread and its impacts.

Interaction with mycorrhiza helper bacterium Streptomyces sp. AcH 505 modifies organisation of actin cytoskeleton in the ectomycorrhizal fungus Amanita muscaria (fly agaric)

The actin cytoskeleton (AC) of fungal hyphae is a major determinant of hyphal shape and morphogenesis, implicated in controlling tip structure and secretory vesicle delivery. Hyphal growth of the ectomycorrhizal fungus Amanita muscaria and symbiosis formation with spruce are promoted by the mycorrhiza helper bacterium Streptomyces sp. AcH 505 (AcH 505). To investigate structural requirements of growth promotion, the effect of AcH 505 on A. muscaria hyphal morphology, AC and actin gene expression were studied. Hyphal diameter and mycelial density decreased during dual culture (DC), and indirect immunofluorescence microscopy revealed that the dense and polarised actin cap in hyphal tips of axenic A. muscaria changes to a loosened and dispersed structure in DC. Supplementation of growth medium with cell-free bacterial supernatant confirmed that reduction in hyphal diameter and AC changes occurred at the same stage of growth. Transcript levels of both actin genes isolated from A. muscaria remained unaltered, indicating that AC changes are regulated by reorganisation of the existing actin pool. In conclusion, the AC reorganisation appears to result in altered hyphal morphology and faster apical extension. The thus improved spreading of hyphae and increased probability to encounter plant roots highlights a mechanism behind the mycorrhiza helper effect.

Structure Elucidation of Auxofuran, a Metabolite Involved in Stimulating Growth of Fly Agaric, Produced by the Mycorrhiza Helper Bacterium Streptomyces AcH 505

Mycorrhiza helper bacterium Streptomyces strain AcH 505 stimulates ectomycorrhiza formation between spruce and fly agaric by supporting fungal growth whereas growth of pathogenic fungi is suppressed. A fungal growth promoting substance was isolated and the chemical structure elucidated by mass spectrometry and NMR spectroscopy. The absolute configuration of the novel fungal growth promoting compound auxofuran (1) was deduced from NMR data with the help of Mosher esters.

[Culture conditions and analysis of amanitins on Amanita spissa]

Isolate of Amanita spissa was obtained from basidiome stipe material collected from environment. It could utilize a broad range of carbon and nitrogen resources. Study on the influence of different conditions for solid culture was carried out. Optimal culture conditions were at 28 degrees C, pH6, in the dark. A. spissa was then fermentated in liquid culture for more mycelia. In flask and Airlift/ff bioreactor, maximum dry mycelia weight of A. spissa reached 0.893 g/L and 2.33 g/L, respectively. Mycelia obtained from solid culture and Airlift/ff bioreactor were then analyzed by HPLC. The results showed that mycelia from both cultures contained amatoxins but no phallotoxins. alpha-Amanitin in mycelia reached 26.02 microg/DWg under solid culture condition, and 15.25 microg/DWg under liquid culture condition. The amanitins were also confirmed by bud-inhibited assay. The results revealed that the effect of amanitin on mung bean cell was identical to that of authentic amanitins. This work suggests that it is possible to produce amatoxin by liquid culturing of A. spissa.

Auxofuran, a novel metabolite that stimulates the growth of fly agaric, is produced by the mycorrhiza helper bacterium Streptomyces strain AcH 505

The mycorrhiza helper bacterium Streptomyces strain AcH 505 improves mycelial growth of ectomycorrhizal fungi and formation of ectomycorrhizas between Amanita muscaria and spruce but suppresses the growth of plant-pathogenic fungi, suggesting that it produces both fungal growth-stimulating and -suppressing compounds. The dominant fungal-growth-promoting substance produced by strain AcH 505, auxofuran, was isolated, and its effect on the levels of gene expression of A. muscaria was investigated. Auxofuran and its synthetic analogue 7-dehydroxy-auxofuran were most effective at a concentration of 15 microM, and application of these compounds led to increased lipid metabolism-related gene expression. Cocultivation of strain AcH 505 and A. muscaria stimulated auxofuran production by the streptomycete. The antifungal substances produced by strain AcH 505 were identified as the antibiotics WS-5995 B and C. WS-5995 B completely blocked mycelial growth at a concentration of 60 microM and caused a cell stress-related gene expression response in A. muscaria. Characterization of these compounds provides the foundation for molecular analysis of the fungus-bacterium interaction in the ectomycorrhizal symbiosis between fly agaric and spruce.

Effect of carbon and nitrogen sources, pH and temperature on in vitro culture of several isolates of Amanita caesarea (Scop.:Fr.) Pers

Several isolates were obtained from sporocarps of Amanita caesarea (Scop.: Fr.) Pers. associated with Quercus suber and Castanea sativa coming from the southwest of Spain. Culture conditions were optimized for these isolates. The largest radial growth was obtained at pH 6-7, and optimal growth temperature was 24-28 degrees C depending on the isolate. Albumin bovine and nitrate produced the largest patch size diameters, but the greatest mycelium dry weight yields were obtained with ammonium. Mannitol produced the largest radial growth, and mannitol and glucose yielded the biggest mycelium dry weights. Although variations in growth behaviour between isolates were observed, only one internal spacer sequence-restriction fragment length polymorphism type was obtained.

The α-tubulin gene AmTuba1: a marker for rapid mycelial growth in the ectomycorrhizal basidiomycete Amanita muscaria

The apical extension of hyphae is of central importance for extensive spread of fungal mycelium in forest soils and for effective ectomycorrhiza development. Since the tubulin cytoskeleton is known to be important for fungal tip growth, we have investigated the expression of an alpha-tubulin gene from the ectomycorrhizal basidiomycete Amanita muscaria (AmTuba1). The phylogenetic analysis of protein sequences revealed the existence of two subgroups of alpha-tubulins in homobasidiomycetes, clearly distinguishable by defined amino acids. AmTuba1 belongs to subgroup1. The AmTuba1 transcript level is related to mycelial growth rate. Growth induction of carbohydrate starved (non-growing) hyphae resulted in an enhanced AmTuba1 expression as soon as hyphal growth started, reaching a maximum at highest mycelial growth rate. Bacterium-induced hyphal elongation also leads to increased AmTuba1 transcript levels. In mature A. muscaria/P. abies ectomycorrhizas, where fungal hyphae are highly branched, and slowly growing, AmTuba1 expression were even lower than in carbohydrate-starved mycelium, indicating a further down-regulation of gene expression in symbiosis. In conclusion, our analyses show that the AmTuba1 gene can be used as a marker for active apical extension in fly agaric, and that alpha-tubulin proteins are promising tools for the classification of fungi.

Production and characterization of Amanitin toxins from a pure culture ofAmanita exitialis

Amanita exitialis Zhu L. Yang and T.H. Li is a lethal mushroom species recently isolated in Guangdong Province, China. In this report, a pure culture of this species was obtained for the first time. To confirm the identity of the pure culture, the internal transcribed spacer regions of the nuclear ribosomal DNA of the pure culture and of a typical fruiting body of the species were sequenced and compared. Further, amatoxins produced by pure cultures were analyzed and characterized by high-performance liquid chromatography and mass spectrometry analysis. The results showed that the pure cultures produced 728.3 +/- 43.8 microg g(-1) (dry matter) of alpha-Amanitin and 60.0 +/- 20.7 microg g(-1) (dry matter) of beta-Amanitin, respectively, a yield which is about 10% of that produced by fruiting bodies.

Release and dispersal of basidiospores from Amanita muscaria var. alba and their infiltration into a residence

Release and dispersal of basidiospores of Amanita muscaria var. alba and their potential to infiltrate a nearby residence were investigated. Basidiospore release mainly occurred in the first three days following the expansion of the caps. The concentrations of released basidiospores near basidiomata were 77 137, 75 062, and 41 738 spores m(-3) in the first three days, respectively, with the highest concentration at 281 738 spores m(-3) air. After three days, the concentration dropped by 95%. At the second location, airborne basidiospore concentrations dropped 96-99% after three days with the concentrations of 940, 575, and 1359 spores m(-3) in the first three days, respectively. The diurnal pattern showed a relatively extended night peak. Relative humidity and dew were positively correlated with basidiospore release and short distance dispersal. Rain and rain rate were positively correlated with basidiospore release, but not correlated with short distance dispersal. The basidiospore release period of Amanita muscaria var. alba was short, but within such a period it released a large amount of basidiospores. However, only less than 5% of basidiospores released were dispersed to the second location 5.2 m away and 2.7 m above the basidiomata. Only < 0.1% of basidiospores dispersed from the basidiomata were found inside a nearby residence. Amanita muscaria var. alba showed a low potential of infiltrating the residence.

Utilisation of inorganic and organic nitrogen sources by Amanita species native to temperate eastern Australia

The abilities of isolates of Amanita alboverrucosa, A. conicoverrucosa, A. fuscosquamosa, A. nauseosa, A. ochrophylla, A. pyramidifera, A. roseolamellata, A. xanthocephala and six unidentified Amanita species from eastern Australian temperate sclerophyll forests to utilise a range of inorganic and organic nitrogen sources for growth was examined in axenic liquid cultures. All taxa utilised NH4+ and at least some amino acids readily, while biomass yields on NO3- and histidine were generally low. All taxa were able to utilise bovine serum albumin, but for most taxa biomass yields on this substrate were significantly lower than on NH4+. Significant intraspecific variation in biomass yield was observed on all substrates for taxa for which multiple isolates were screened. As a group, eastern Australian Amanita species thus have the potential to utilise nitrogen from a broad range of organic substrates and this might be important in the nitrogen nutrition of their ectomycorrhizal tree hosts in sclerophyll forests.

Utilisation of inorganic and organic nitrogen sources by Amanita species native to temperate eastern Australia

The abilities of isolates of Amanita alboverrucosa, A. conicoverrucosa, A. fuscosquamosa, A. nauseosa, A. ochrophylla, A. pyramidifera, A. roseolamellata, A. xanthocephala and six unidentified Amanita species from eastern Australian temperate sclerophyll forests to utilise a range of inorganic and organic nitrogen sources for growth was examined in axenic liquid cultures. All taxa utilised NH4+ and at least some amino acids readily, while biomass yields on NO3- and histidine were generally low. All taxa were able to utilise bovine serum albumin, but for most taxa biomass yields on this substrate were significantly lower than on NH4+. Significant intraspecific variation in biomass yield was observed on all substrates for taxa for which multiple isolates were screened. As a group, eastern Australian Amanita species thus have the potential to utilise nitrogen from a broad range of organic substrates and this might be important in the nitrogen nutrition of their ectomycorrhizal tree hosts in sclerophyll forests.

Influence of copper, manganese and pH on the growth and several enzyme activities in mycorrhizal fungus Amanita muscaria

The effects of various concentrations of copper, manganese and pH on the growth and several enzyme activities of mycorrhizal fungus Amanita muscaria were investigated. Cu (5-25 mg l-1) and lower pH (3.0-4.0) strongly inhibited the mycelial growth (dry weight), however, the protein content was not affected evidently. Some enzyme activities were lower as the Cu and Mn concentrations were higher and other enzymes had the maximum values at the specified concentration. The activities of the following enzymes were significantly correlated with the fungal growth after the treatment with Cu: G6PDH, MTLDH and trehalase, and with Mn: G6PDH, MTLDH and alpha-mannosidase respectively. Measurement of these enzyme activities might provide a useful biochemical criterion for the evaluation of the fungitoxicity of soil contaminated by copper or manganese.

Amanita phalloides in Victoria

Amanita phalloides is found regularly in suburban Melbourne and country areas where old oaks and other deciduous trees are grown as street trees, in parks, and in private gardens. This deadly poisonous mushroom may be mistaken for the edible Agaricus spp.