Amanita phalloides
1. Classification
a. Higher order taxa
Eukaryota; Basidiomycota; Agaricomycetes; Agaricales; Amanitaceae; Amanita
Species
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NCBI: [1] |
Amanita phalloides
2. Description and significance
Amanita phalloides, commonly known as death cap, is a fungus native to Europe that was introduced to many other regions of the world in the late 20th century (2). A. phalloides is responsible for the majority of mushroom poisoning-related deaths in humans (3). The primary compound released is 𝛼-Amanitin, which causes liver and kidney failure after ingestion and cannot be removed via cooking (3). There is no direct antidote for A. phalloides, making it dangerous to humans as its appearance is similar to common edible mushrooms (4). Because of its high toxicity and fatality rate in humans, research focuses on better treatments (5).
3. Genome structure
The genome of A. phalloides has been fully sequenced (6). The assembly size is 40 Mb with 5,437 contigs (6). There are 10221 gene models, of which 8177 are annotated (6). The average predicted transcript length is 1494 bp and has an average of 49% GC content (6). The genes AMA1 and PHA1, responsible for α-amanitin and phallacidin synthesis, are exclusive to toxic Amanita mushrooms in the Phalloideae group, such as A. phalloides (7). The toxic genes, MSDIN, produce α-amanitin, phalloidin, and phallacidin (8). MSDIN are physically clustered in the fungal genome, showing higher genetic similarity within the cluster compared to genes elsewhere in the genome (8). A. phalloides encodes more than 50 cyclic peptides to synthesize amatoxins, phallotoxins, and antamanide (6). The mitochondrial genome size of A. phalloides is 101,106 bp and contains 34 non-intronic protein-coding genes (9). The mitogenome has a GC content of 24.56% and a positive AT skew. (9) The mitogenome has 27 tRNAs and 2 rRNAs with the small subunit ribosomal RNA containing one intron and the large subunit ribosomal RNA containing four introns (9). There are 51 repeat sequences accounting for 10.26% of the total mitogenome (9). The protein coding region consists of 28245 bp, accounting for 27.94% of the genome (9).
4. Cell structure
Major physical characteristics of A. phalloides include white gills, a thin skirt membrane, and protruding from a cup-like structure (10). A. phalloides has an ovular cap varying from 4cm to 16cm in diameter (11). The mushroom typically ranges in color from yellow to brown and is finely and innately streaked (11). The white stem ranges from 5cm to 18cm long, tapers to an apex, and flares to a base that is encased by a sac-like white volva. Gills are free from the stem and crowded together (11). Microscopically, A. phalloides contain smooth, ellipsoid, and fibrous spores approximately 12x10μm in size (11).
5. Metabolic processes
A. phalloides is an ectomycorrhizal fungus; ectomycorrhizal fungi are obligate symbionts (2). A. phalloides grows in association with tree roots which provide carbon if the fungus provides other nutrients like nitrogen and phosphorus (12). Ectomycorrhizal fungi are obligate aerobes and heterotrophs (13) (14). It was previously thought that ectomycorrhizal fungi were facultative saprotrophs that could decompose organic matter for reduced carbon compounds when host plants did not provide enough (15). However, this hypothesis has been questioned (15). Ectomycorrhizal fungi have limited and varied ability to decompose organic matter (15). Although with host sugars from plants, ectomycorrhizal fungi perform co-metabolic decomposition of organic matter to increase nitrogen mobilization rather than carbon metabolic products (15). A. phalloides has not been maintained in an artificial medium (16). A. phalloides produces amatoxins, phallotoxins, and virotoxins (3). Amatoxins produced by A. phalloides greatly reduce protein synthesis in other organisms by binding to RNA polymerase II, inhibiting its activity and thus mRNA transcription (3). Phallotoxins produced by A. phalloides bind to F-actin in other organisms which causes abnormal cytoskeleton function due to actin filament stabilization and microfilament depolymerization inhibition (3). Amatoxins and phallotoxins are coded by the two genes AMA1 and PHA1 respectively (17). The toxins are synthesized as proproteins which are processed by prolyl oligopeptidase enzymes and undergo other biosynthetic steps that have not been well documented yet (17). The mechanisms of virotoxins have yet to be clearly defined, though they are considered less significant due to poor oral absorption in humans (3).
6. Ecology
A. phalloides is native to Europe, where it is widely dispersed across northeastern Europe, North Africa, and western Russia (18). Over time, the fungus has been introduced to places like Australia, Southern Africa, South America, and North America, presumably on the roots of imported plants (2). In North America, A. phalloides is found on the West Coast from Southern California to Vancouver Island, and on the East Coast from Maryland to New Hampshire and Maine (19). A. phalloides is an ectomycorrhizal fungus that relies on a symbiotic relationship with the roots of plant species such as oak and conifer trees (18). The plant provides carbon and shelter to the fungus, while the fungus provides nutrients like nitrogen and phosphorus to the plant (12). As the fungus has expanded across the globe, A. phalloides has been observed with species other than the English oak tree, its most common associate in Europe (18). In North America, A. phalloides associates mainly with conifer trees on the East Coast and oak trees on the West Coast (18). These host changes can have significant effects on A. phalloides, such as mushrooms growing twice as large in California (18). A. phalloides is described as an invasive symbiont which is a symbiont that has developed new associations in new geographical locations (2).
7. Pathology
A. phalloides is toxic to most known living organisms when ingested, with its toxin (primarily amatoxins) wreaking havoc on many different bodily systems (3). The poisoning symptoms can range from gastrointestinal discomfort to death, as the toxin mainly affects the liver and kidneys. The progression of illness is carried out in the first 6-24 hours after ingestion and is characterized by nausea, abdominal pain, bloody stools, and urine (3). After detectable symptoms are resolved, if the toxin continues to function, extreme cases result in internal bleeding. The final stage involves close-to-complete liver and kidney failure with possible deterioration of the central nervous system (3). The basis of the current treatment plan involves general detoxification, as there is no antidote for any of the toxins present in A. phalloides (20). The disappearance of detectable symptoms makes treatment more difficult. For the detoxification procedures, clinicians have focused on a layered approach, focusing on mouth, urine, and liver detoxification (20). If the poisoning progresses to the point of liver failure or beyond, liver transplantation or other more invasive surgeries may be required to attempt to cure the patient. Chemotherapy might also be effective in these extreme cases (20).
8. Current Research
Current research on A. phalloides focuses on potential treatments for the 𝛼-Amanitin toxin. In 2022, patients in Italy who experienced mushroom poisoning by A. phalloides were treated with activated charcoal and N-acetyl cysteine with success (21). In 2023, a combination treatment with N-acetyl cysteine and silibinin found mixed success (22). Silibinin is utilized as a possible antidote in Europe and is undergoing clinical trials in the United States (4)(23). The main treatment of patients focuses on supportive management to clear the toxin as no specific antidote exists (20). In 2023, combination therapy of fluid resuscitation, plasma exchange, benzylpenicillin, and N-acetylcysteine proved effective in managing poisoning (24). The most lethal component of A. phalloides is 𝛼-Amanitin with STT3B being an important requirement for 𝛼-Amanitin toxicity (5). In 2023, Indocyanine green was successful in inhibiting STT3B and blocking the effects of the toxin in cells, increasing the potential survival rate, as the newest potential treatment (5).
9. References
(1) Schoch, C. L., Ciufo, S., Domrachev, M., Hotton, C. L., Kannan, S., Khovanskaya, R., Leipe, D., Mcveigh, R., O’Neill, K., Robbertse, B., Sharma, S., Soussov, V., Sullivan, J. P., Sun, L., Turner, S., & Karsch-Mizrachi, I. (2020). NCBI taxonomy: A comprehensive update on curation, resources and Tools. Database, 2020. https://doi.org/10.1093/database/baaa062
(2) Pringle, A., Adams, R. I., Cross, H. B., & Bruns, T. D. (2009). The ectomycorrhizal fungus amanita phalloides was introduced and is expanding its range on the west coast of North America. Molecular Ecology, 18(5), 817–833. https://doi.org/10.1111/j.1365-294x.2008.04030.x
(3) Garcia, J., Costa, V. M., Carvalho, A., Baptista, P., de Pinho, P. G., de Lourdes Bastos, M., & Carvalho, F. (2015). Amanita phalloides poisoning: Mechanisms of toxicity and treatment. Food and Chemical Toxicology : An International Journal Published for the British Industrial Biological Research Association, 86, 41–55. https://doi.org/10.1016/j.fct.2015.09.008
(4) Vo, K. T., Montgomery, M. E., Mitchell, S. T., Scheerlinck, P. H., Colby, D. K., Meier, K. H., Kim-Katz, S., Anderson, I. B., Offerman, S. R., Olson, K. R., & Smollin, C. G. (2017). Amanita phalloides Mushroom Poisonings - Northern California, December 2016. MMWR. Morbidity and Mortality Weekly Report, 66(21), 549–553. https://doi.org/10.15585/mmwr.mm6621a1
(5) Wang, B., Wan, A. H., Xu, Y., Zhang, R.-X., Zhao, B.-C., Zhao, X.-Y., Shi, Y.-C., Zhang, X., Xue, Y., Luo, Y., Deng, Y., Neely, G. G., Wan, G., & Wang, Q.-P. (2023). Identification of indocyanine green as a STT3B inhibitor against mushroom α-amanitin cytotoxicity. Nature Communications, 14(1), 2241.
(6) Pulman, J. A., Childs, K. L., Sgambelluri, R. M., & Walton, J. D. (2016). Expansion and diversification of the MSDIN family of cyclic peptide genes in the poisonous agarics amanita phalloides and A. Bisporigera. BMC Genomics, 17(1). https://doi.org/10.1186/s12864-016-3378-7
(7) Hallen, H. E., Luo, H., Scott-Craig, J. S., & Walton, J. D. (2007). Gene family encoding the major toxins of lethal Amanita mushrooms. Proceedings of the National Academy of Sciences, 104(48), 19097-19101.
(8) Drott, M. T., Park, S. C., Wang, Y.-W., Harrow, L., Keller, N. P., & Pringle, A. (2023). Pangenomics of the death cap mushroom Amanita phalloides, and of Agaricales, reveals dynamic evolution of toxin genes in an invasive range. The ISME Journal, 17(8), 1236–1246. https://doi.org/10.1038/s41396-023-01432-x
(9) Li, Q., He, X., Ren, Y., Xiong, C., Jin, X., Peng, L., & Huang, W. (2020). Comparative mitogenome analysis reveals mitochondrial genome differentiation in ectomycorrhizal and asymbiotic amanita species. Frontiers in Microbiology, 11. https://doi.org/10.3389/fmicb.2020.01382
(10) Sisodiya, A. S., Kadicheeni, A. S., Das, G., Kumari, T., TS, A., & Kumar, D. (2023). How to tell the mushroom you are holding will kill you or heal you: A mini review. The Pharma Innovation, 12(2), 109–122.
(11) Codjia, J. E., Cai, Q., Zhou, S. W., Luo, H., Ryberg, M., Yorou, N. S., & Yang, Z. L. (2020). Morphology, multilocus phylogeny, and toxin analysis reveal amanita albolimbata, the first lethal amanita species from Benin, West Africa. Frontiers in Microbiology, 11. https://doi.org/10.3389/fmicb.2020.599047
(12) Tedersoo, L., May, T. W., & Smith, M. E. (2010). Ectomycorrhizal lifestyle in fungi: global diversity, distribution, and evolution of phylogenetic lineages. Mycorrhiza, 20(4), 217–263. https://doi.org/10.1007/s00572-009-0274-x
(13) Prendergast-Miller, M. T., Baggs, E. M., & Johnson, D. (2011). Nitrous oxide production by the ectomycorrhizal fungi Paxillus involutus and Tylospora fibrillosa. FEMS Microbiology Letters, 316(1), 31–35. https://doi.org/10.1111/j.1574-6968.2010.02187.x
(14) Taylor, T. N., & Osborn, J. M. (1996). The importance of fungi in shaping the paleoecosystem. Review of Palaeobotany and Palynology, 90(3), 249–262. https://doi.org/https://doi.org/10.1016/0034-6667(95)00086-0
(15) Lindahl, B. D., & Tunlid, A. (2015). Ectomycorrhizal fungi – potential organic matter decomposers, yet not saprotrophs. New Phytologist, 205(4), 1443–1447. https://doi.org/https://doi.org/10.1111/nph.13201
(16) Luo, H., DuBois, B., Sgambelluri, R. M., Angelos, E. R., Li, X., Holmes, D., & Walton, J. D. (2015). Production of 15N-labeled α-amanitin in Galerina marginata. Toxicon, 103, 60–64. https://doi.org/https://doi.org/10.1016/j.toxicon.2015.06.018
(17) Walton, J. (2018). Biosynthesis of the Amanita Cyclic Peptide Toxins BT - The Cyclic Peptide Toxins of Amanita and Other Poisonous Mushrooms (J. Walton (Ed.); pp. 93–130). Springer International Publishing. https://doi.org/10.1007/978-3-319-76822-9_4
(18) Wolfe, B. E., & Pringle, A. (2012). Geographically structured host specificity is caused by the range expansions and host shifts of a symbiotic fungus. The ISME Journal, 6(4), 745–755. https://doi.org/10.1038/ismej.2011.155
(19) Wolfe, B. E., Richard, F., Cross, H. B., & Pringle, A. (2010). Distribution and abundance of the introduced ectomycorrhizal fungus Amanita phalloides in North America. New Phytologist, 185(3), 803–816. https://doi.org/https://doi.org/10.1111/j.1469-8137.2009.03097.x
(20) Santi, L., Maggioli, C., Mastroroberto, M., Tufoni, M., Napoli, L., & Caraceni, P. (2012). Acute Liver Failure Caused by Amanita phalloides Poisoning. International Journal of Hepatology, 2012. https://doi.org/10.1155/2012/487480
(21) Al-Husinat, L. M., Ferrara. G., Alsabbah A., Cotoia, A., & Beck., R. (2022). Amanita Phalloides Poisoning, Early Activated Charcoal plys N-Acetyl Cysteine Treatment: Case Report and a Brief Literature Review. Acta Med Croatica, 76, 281-287.
(22) Iskander, P., Marzouk, D., Iskander, A., & Oza, F. (2023). Malicious mushrooms. Gastro Hep Advances, 2(4), 544–546. https://doi.org/10.1016/j.gastha.2023.01.012
(23) Mylan Specialty, LP. (2009, November 10). Intravenous Milk Thistle (Silibinin-Legalon) for Hepatic Failure Induced by Amatoxin/Amanita Mushroom Poisoning. CTG Labs - NCBI. https://www.clinicaltrials.gov/study/NCT00915681
(24) Hassan, W. (2023). Amanita phalloides mushroom poisoning: A case report. Journal of Medical Case Reports and Case Series, 4(1). https://doi.org/10.38207/jmcrcs/2023/jan04010405
Edited by Isabella Coady, Gerely De Los Santos Aristy, William Fan, Rachel Gelven, and Jia Yuan, students of Jennifer Bhatnagar for BI 311 General Microbiology, 2023, Boston University.
