Amanita exitialis
Encyclopedia
Amanita exitialis, also known as the Guangzhou destroying angel, is a mushroom
of the large genus Amanita
. It is distributed in eastern Asia, and probably also in India where it has been misidentified as A. verna
. Deadly poisonous, it is a member of section Phalloideae and related to the death cap A. phalloides. The fruit bodies
(mushrooms) are white, small to medium-sized with caps
up to 7 cm (2.8 in) in diameter, a somewhat friable ring
and a firm volva
. Unlike most agaric
mushrooms which typically have four-spored basidia (spore-bearing cells), the basidia of A. exitialis are almost entirely two-spored. Eight people were fatally poisoned in China after consuming the mushroom in 2000, and another 20 have been fatally poisoned since that incident. Molecular analysis shows that the species has a close phylogenetic relationship with three other toxic white Amanitas: A. subjunquillea
var. alba, A. virosa
and A. bisporigera
.
specimens of white Amanita typically referred to as either A. verna
or A. virosa
. They realized that collections referred to as these European species actually comprised three taxa
new to science or the region. The holotype
specimen of A. exitialis is located in the Mycological Herbarium of Guangdong Institute of Microbiology.
In 2005, Zhang and colleagues performed a phylogenetic analysis based on the ITS
sequences of several white-bodied toxic Amanita species. Their results support a clade
containing four lethal Amanita species with white fruit bodies. A. exitialis has two-spored basidia similar to the North American species A. bisporigera
, but A. exitialis has a closer phylogenetic relationship with Amanita subjunquillea var. alba
, a four-spored white lethal species from China. The specific epithet exitialis derives from the Latin
word "destructive", and refers to the lethally poisonous nature of the mushroom.
Amanita exitialis is classified in the section Phalloideae of the genus Amanita
. Species of this section share the following characteristics: spores that are not strongly elongated, and never with a cyclindric shape; flesh not reddening upon bruising; lamellulae (short gills that do not reach the edge of the cap) abruptly cut off; a well-formed pouch- or sac-like membranous volva
. All species of Phalloideae are ectomycorrhizal and contain amatoxins.
The cap
is 4 – in diameter, initially egg-shaped, then convex but flattening with age, and sometimes slightly depressed at the center. The cap surface is smooth, white, but cream-colored in the center. The margin (cap edge) is non-striate, non-appendiculate (without any partial veil
remnants hanging along the cap margin); the flesh
white. The gills are free from attachment to the stem, white to whitish, crowded closely together, and up to 5 mm in height. The lamellulae are long and tapering, plentiful, and arranged in 2–3 tiers. The stem
is 7 – by 0.5 –, roughly cylindrical or slightly tapering upward, with apex slightly expanded. The surface is white to whitish, smooth, or sometimes with fibrous small scales. The bulb at the base of the stem is roughly spherical and 1 – wide. The volva
is limbate (has a distinct edge), thin, membranous, with free limb up to 7 mm in height, and both surfaces are white. The ring
is near the top of the stem, thin, membranous, white, persistent or may be torn from the stem during expansion of the cap. All tissues of the fruit body will turn yellow if a drop of dilute potassium hydroxide
is applied.
The spore
s are spherical or nearly so, rarely broadly ellipsoid, and measure 9.5–12 by 9–11.5 µm
. They are hyaline
(translucent) and colorless, amyloid
(absorbing iodine
when stained with Melzer's reagent
), thin-walled, smooth, and have a small apiculus. The spore-bearing cells, the basidia, are 27–55 by 10–15 µm, club-shaped, and two-spored (rarely one-spored). They have sterigmata (slender projections that attach the spores) that are 5–7 µm long.
n Amanita species, the authors mention several collections identified as A. verna
, from various locations in the Indian provinces Maharashtra
, Orissa
, and Rajasthan
. As Bhatt et al. explain, the material collected by Dhanchiola in Orissa and identified as A. virosa has two-spored basidia, and his description matches that of A. exitialis.
Field observations suggest that the mushroom associates mycorrhiza
lly with the plant Castanopsis fissa, a deciduous
tree found only in the southern provinces of China, such as Guangdong
, Yunnan
and Hunan
. Mushroom fruitings are abundant in the warm spring rains of March and April, although they are also seen in May to July.
s (alpha-amanitin
, beta-amanitin
) and phallotoxin
s (phallacidin, phallisin, phalloin, phalloidin) in the three tissues (cap, stipe and volva) of Amanita exitialis have been determined using high-performance liquid chromatography
. The cap had the highest content of total toxins, reaching over 8000 µg
/g dry weight
(µg of toxin per gram of dried tissue), the toxins content in the stem was over 3700 µg/g dry weight, whereas the volva had the lowest content of total toxins, with about 1150 µg/g dry weight. Amatoxins content (alpha-amanitin and beta-amanitins especially alpha-amanitin) in the cap, stem or volva of A. exitialis was higher than that of Phallotoxins (Phallacidin, Phallisin, Phalloidin and Phalloin), but the content of phallotoxins (especially phallacidin) was gradually higher from cap to stem and to volva. A 2011 study reported the presence of additional toxins amaninamide
, phallacin, phallisacin and desoxoviridin. A Chinese study concluded that this species had the highest mortality rate of all toxic mushrooms in China. It has been estimated that about 50 grams (1.8 oz) of fresh mushrooms contains sufficient toxin to cause the death of a 50 kilograms (110.2 lb) adult. In March 2000, nine people consumed the mushroom in Guangzhou
, and only one survived. Since 2000, another 20 people have died in the southern provinces of China from consuming the mushroom.
Toxic peptides from Amanita species have been widely used in biological research as chemical agents to inhibit RNA polymerase II
, an enzyme
essential for protein synthesis. However, these toxic peptides can only be obtained from fruit bodies collected from natural habitats, and are consequently expensive. Some success has been reported in extracting peptide toxins directly from the mycelia of Amanita exitialis grown in liquid culture
. Although the toxin concentration in the mycelium is only about 10% of that in fruiting bodies, the authors suggest that is possible to increase the amatoxin production by optimizing the growth conditions.
nucleoside
that is coupled with an amino acid
derivative
named N2-(1-methoxycarbonylethyl)guanosine. The discovery and identification of this chemical was the first report of a naturally occurring nucleoside in which an amino acid derivative is bonded through its α-amino nitrogen
(the nitrogen bonded to the α-carbon) to a nucleobase
aglycone
by a C-N (carbon to nitrogen) bond. The new compound was determined to be toxic in the brine shrimp lethality test, but it did not have cytotoxic activity against a variety of human cancer cell lines
. Other compounds isolated from the fungus include β-carboline
and russulaceramide (a ceramide
formerly found in some Russula
mushrooms).
Mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
of the large genus Amanita
Amanita
The genus Amanita contains about 600 species of agarics including some of the most toxic known mushrooms found worldwide. This genus is responsible for approximately 95% of the fatalities resulting from mushroom poisoning, with the death cap accounting for about 50% on its own...
. It is distributed in eastern Asia, and probably also in India where it has been misidentified as A. verna
Amanita verna
Amanita verna, commonly known as the fool's mushroom, Destroying angel or the mushroom fool, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Occurring in Europe in spring, A. verna associates with various deciduous and coniferous trees...
. Deadly poisonous, it is a member of section Phalloideae and related to the death cap A. phalloides. The fruit bodies
Basidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...
(mushrooms) are white, small to medium-sized with caps
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
up to 7 cm (2.8 in) in diameter, a somewhat friable ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
and a firm volva
Volva (mycology)
The volva is a mycological term to describe a cup-like structure at the base of a mushroom that is a remnant of the universal veil. This macrofeature is important in wild mushroom identification due to it being an easily observed, taxonomically significant feature which frequently signifies a...
. Unlike most agaric
Agaric
An agaric is a type of fungal fruiting body characterized by the presence of a pileus that is clearly differentiated from the stipe , with lamellae on the underside of the pileus. "Agaric" can also refer to a basidiomycete species characterized by an agaric-type fruiting body...
mushrooms which typically have four-spored basidia (spore-bearing cells), the basidia of A. exitialis are almost entirely two-spored. Eight people were fatally poisoned in China after consuming the mushroom in 2000, and another 20 have been fatally poisoned since that incident. Molecular analysis shows that the species has a close phylogenetic relationship with three other toxic white Amanitas: A. subjunquillea
Amanita subjunquillea
Amanita subjunquillea, also known as the East Asian death cap is a mushroom of the large genus Amanita, which occurs in East and Southeast Asia. Deadly poisonous, it is a member of section phalloideae and related to the death cap A. phalloides.Initially little reported, the toxicity of A...
var. alba, A. virosa
Amanita virosa
Amanita virosa, commonly known as the European destroying angel, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Occurring in Europe, A. virosa associates with various deciduous and coniferous trees...
and A. bisporigera
Amanita bisporigera
Amanita bisporigera is a deadly poisonous species of fungus in the Amanitaceae family. It is commonly known as the eastern North American destroying angel or the destroying angel, although it shares this latter name with three other lethal white Amanita species, A. ocreata, A. verna and...
.
Taxonomy, classification, and phylogeny
Zhu-Liang Yang and Tai-Hui Li discovered the species by reexamining various herbariumHerbarium
In botany, a herbarium – sometimes known by the Anglicized term herbar – is a collection of preserved plant specimens. These specimens may be whole plants or plant parts: these will usually be in a dried form, mounted on a sheet, but depending upon the material may also be kept in...
specimens of white Amanita typically referred to as either A. verna
Amanita verna
Amanita verna, commonly known as the fool's mushroom, Destroying angel or the mushroom fool, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Occurring in Europe in spring, A. verna associates with various deciduous and coniferous trees...
or A. virosa
Amanita virosa
Amanita virosa, commonly known as the European destroying angel, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Occurring in Europe, A. virosa associates with various deciduous and coniferous trees...
. They realized that collections referred to as these European species actually comprised three taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
new to science or the region. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen of A. exitialis is located in the Mycological Herbarium of Guangdong Institute of Microbiology.
In 2005, Zhang and colleagues performed a phylogenetic analysis based on the ITS
Internal transcribed spacer
ITS refers to a piece of non-functional RNA situated between structural ribosomal RNAs on a common precursor transcript. Read from 5' to 3', this polycistronic rRNA precursor transcript contains the 5' external transcribed sequence , 18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA and finally the 3'ETS...
sequences of several white-bodied toxic Amanita species. Their results support a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
containing four lethal Amanita species with white fruit bodies. A. exitialis has two-spored basidia similar to the North American species A. bisporigera
Amanita bisporigera
Amanita bisporigera is a deadly poisonous species of fungus in the Amanitaceae family. It is commonly known as the eastern North American destroying angel or the destroying angel, although it shares this latter name with three other lethal white Amanita species, A. ocreata, A. verna and...
, but A. exitialis has a closer phylogenetic relationship with Amanita subjunquillea var. alba
Amanita subjunquillea
Amanita subjunquillea, also known as the East Asian death cap is a mushroom of the large genus Amanita, which occurs in East and Southeast Asia. Deadly poisonous, it is a member of section phalloideae and related to the death cap A. phalloides.Initially little reported, the toxicity of A...
, a four-spored white lethal species from China. The specific epithet exitialis derives from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
word "destructive", and refers to the lethally poisonous nature of the mushroom.
Amanita exitialis is classified in the section Phalloideae of the genus Amanita
Amanita
The genus Amanita contains about 600 species of agarics including some of the most toxic known mushrooms found worldwide. This genus is responsible for approximately 95% of the fatalities resulting from mushroom poisoning, with the death cap accounting for about 50% on its own...
. Species of this section share the following characteristics: spores that are not strongly elongated, and never with a cyclindric shape; flesh not reddening upon bruising; lamellulae (short gills that do not reach the edge of the cap) abruptly cut off; a well-formed pouch- or sac-like membranous volva
Volva (mycology)
The volva is a mycological term to describe a cup-like structure at the base of a mushroom that is a remnant of the universal veil. This macrofeature is important in wild mushroom identification due to it being an easily observed, taxonomically significant feature which frequently signifies a...
. All species of Phalloideae are ectomycorrhizal and contain amatoxins.
Description
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
is 4 – in diameter, initially egg-shaped, then convex but flattening with age, and sometimes slightly depressed at the center. The cap surface is smooth, white, but cream-colored in the center. The margin (cap edge) is non-striate, non-appendiculate (without any partial veil
Partial veil
thumb|150px|right|Developmental stages of [[Agaricus campestris]] showing the role and evolution of a partial veilPartial veil is a mycological term used to describe a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics...
remnants hanging along the cap margin); the flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
white. The gills are free from attachment to the stem, white to whitish, crowded closely together, and up to 5 mm in height. The lamellulae are long and tapering, plentiful, and arranged in 2–3 tiers. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
is 7 – by 0.5 –, roughly cylindrical or slightly tapering upward, with apex slightly expanded. The surface is white to whitish, smooth, or sometimes with fibrous small scales. The bulb at the base of the stem is roughly spherical and 1 – wide. The volva
Volva (mycology)
The volva is a mycological term to describe a cup-like structure at the base of a mushroom that is a remnant of the universal veil. This macrofeature is important in wild mushroom identification due to it being an easily observed, taxonomically significant feature which frequently signifies a...
is limbate (has a distinct edge), thin, membranous, with free limb up to 7 mm in height, and both surfaces are white. The ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
is near the top of the stem, thin, membranous, white, persistent or may be torn from the stem during expansion of the cap. All tissues of the fruit body will turn yellow if a drop of dilute potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
is applied.
The spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s are spherical or nearly so, rarely broadly ellipsoid, and measure 9.5–12 by 9–11.5 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
. They are hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
(translucent) and colorless, amyloid
Amyloid (mycology)
In mycology the term amyloid refers to a crude chemical test using iodine in either Melzer's reagent or Lugol's solution, to produce a black to blue-black positive reaction. It is called amyloid because starch gives a similar reaction, and that reaction for starch is also called an amyloid reaction...
(absorbing iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
when stained with Melzer's reagent
Melzer's Reagent
Melzer's reagent is a chemical reagent used by mycologists to assist with the identification of fungi.-Composition:...
), thin-walled, smooth, and have a small apiculus. The spore-bearing cells, the basidia, are 27–55 by 10–15 µm, club-shaped, and two-spored (rarely one-spored). They have sterigmata (slender projections that attach the spores) that are 5–7 µm long.
Similar species
Amanita exitialis is similar to A. bisporigera, a species originally described by George Francis Atkinson from the United States. In comparison to A. exitialis, A. bisporigera differs by its lower placement of the ring on the stem, smaller spores (typically 8–9.5 by 7–8.5 µm), and different structure of the volva. American specimens of A. bisporigera have more abundant inflated cells than that of A. exitialis. Two other white Asian species, A. oberwinklerana and A. subjunquillea var. alba also resemble A. exitialis, but are four-spored.Habitat and distribution
The fruit bodies of A. exitialis grow solitarily or in groups on the ground in coniferous forests. It is known only from the type locality, Guangdong Province. In a 2003 survey of IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
n Amanita species, the authors mention several collections identified as A. verna
Amanita verna
Amanita verna, commonly known as the fool's mushroom, Destroying angel or the mushroom fool, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Occurring in Europe in spring, A. verna associates with various deciduous and coniferous trees...
, from various locations in the Indian provinces Maharashtra
Maharashtra
Maharashtra is a state located in India. It is the second most populous after Uttar Pradesh and third largest state by area in India...
, Orissa
Orissa
Orissa , officially Odisha since Nov 2011, is a state of India, located on the east coast of India, by the Bay of Bengal. It is the modern name of the ancient nation of Kalinga, which was invaded by the Maurya Emperor Ashoka in 261 BC. The modern state of Orissa was established on 1 April...
, and Rajasthan
Rajasthan
Rājasthān the land of Rajasthanis, , is the largest state of the Republic of India by area. It is located in the northwest of India. It encompasses most of the area of the large, inhospitable Great Indian Desert , which has an edge paralleling the Sutlej-Indus river valley along its border with...
. As Bhatt et al. explain, the material collected by Dhanchiola in Orissa and identified as A. virosa has two-spored basidia, and his description matches that of A. exitialis.
Field observations suggest that the mushroom associates mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
lly with the plant Castanopsis fissa, a deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
tree found only in the southern provinces of China, such as Guangdong
Guangdong
Guangdong is a province on the South China Sea coast of the People's Republic of China. The province was previously often written with the alternative English name Kwangtung Province...
, Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
and Hunan
Hunan
' is a province of South-Central China, located to the south of the middle reaches of the Yangtze River and south of Lake Dongting...
. Mushroom fruitings are abundant in the warm spring rains of March and April, although they are also seen in May to July.
Toxicity
The content and distribution of the main amatoxinAmatoxin
Amatoxins are a subgroup of at least eight toxic compounds found in several genera of poisonous mushrooms, most notably Amanita phalloides and several other members of the genus Amanita, as well as some Conocybe, Galerina and Lepiota mushroom species.-Structure:The compounds have a similar...
s (alpha-amanitin
Alpha-amanitin
alpha-Amanitin or α-amanitin is a cyclic peptide of eight amino acids. It is possibly the most deadly of all the amatoxins, toxins found in several species of the Amanita genus of mushrooms, one being the Death cap as well as the Destroying angel, a complex of similar species, principally A....
, beta-amanitin
Beta-amanitin
beta-Amanitin or β-amanitin is a cyclic peptide of eight amino acids. It is an amatoxin, a group of toxins isolated from and found in several members of the Amanita genus of mushrooms, one being the Death cap as well as the Destroying angel, a complex of similar species, principally A. virosa...
) and phallotoxin
Phallotoxin
The phallotoxins consist of at least seven compounds, all of which are bicyclic heptapeptides , isolated from the death cap . Phalloidin had been isolated in 1937 by Feodor Lynen, Heinrich Wieland's student and son-in-law, and Ulrich Wieland of the University of Munich...
s (phallacidin, phallisin, phalloin, phalloidin) in the three tissues (cap, stipe and volva) of Amanita exitialis have been determined using high-performance liquid chromatography
High-performance liquid chromatography
High-performance liquid chromatography , HPLC, is a chromatographic technique that can separate a mixture of compounds and is used in biochemistry and analytical chemistry to identify, quantify and purify the individual components of the mixture.HPLC typically utilizes different types of stationary...
. The cap had the highest content of total toxins, reaching over 8000 µg
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
/g dry weight
Dry matter
The dry matter is a measurement of the mass of something when completely dried.The dry matter of plant and animal material would be its solids, i.e. all its constituents excluding water. The dry matter of food would include carbohydrates, fats, proteins, vitamins, minerals, and antioxidants...
(µg of toxin per gram of dried tissue), the toxins content in the stem was over 3700 µg/g dry weight, whereas the volva had the lowest content of total toxins, with about 1150 µg/g dry weight. Amatoxins content (alpha-amanitin and beta-amanitins especially alpha-amanitin) in the cap, stem or volva of A. exitialis was higher than that of Phallotoxins (Phallacidin, Phallisin, Phalloidin and Phalloin), but the content of phallotoxins (especially phallacidin) was gradually higher from cap to stem and to volva. A 2011 study reported the presence of additional toxins amaninamide
Amaninamide
Amaninamide is a cyclic nonribosomal peptide. It is one of the amatoxins, all of which are found in several members of the Amanita genus of mushrooms.-Toxicology:Like other amatoxins, amaninamide is an inhibitor of RNA polymerase II...
, phallacin, phallisacin and desoxoviridin. A Chinese study concluded that this species had the highest mortality rate of all toxic mushrooms in China. It has been estimated that about 50 grams (1.8 oz) of fresh mushrooms contains sufficient toxin to cause the death of a 50 kilograms (110.2 lb) adult. In March 2000, nine people consumed the mushroom in Guangzhou
Guangzhou
Guangzhou , known historically as Canton or Kwangchow, is the capital and largest city of the Guangdong province in the People's Republic of China. Located in southern China on the Pearl River, about north-northwest of Hong Kong, Guangzhou is a key national transportation hub and trading port...
, and only one survived. Since 2000, another 20 people have died in the southern provinces of China from consuming the mushroom.
Toxic peptides from Amanita species have been widely used in biological research as chemical agents to inhibit RNA polymerase II
RNA polymerase II
RNA polymerase II is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase...
, an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
essential for protein synthesis. However, these toxic peptides can only be obtained from fruit bodies collected from natural habitats, and are consequently expensive. Some success has been reported in extracting peptide toxins directly from the mycelia of Amanita exitialis grown in liquid culture
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
. Although the toxin concentration in the mycelium is only about 10% of that in fruiting bodies, the authors suggest that is possible to increase the amatoxin production by optimizing the growth conditions.
Bioactive compounds
The fruit bodies of Amanita exitialis contain a unique purinePurine
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
nucleoside
Nucleoside
Nucleosides are glycosylamines consisting of a nucleobase bound to a ribose or deoxyribose sugar via a beta-glycosidic linkage...
that is coupled with an amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
derivative
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...
named N2-(1-methoxycarbonylethyl)guanosine. The discovery and identification of this chemical was the first report of a naturally occurring nucleoside in which an amino acid derivative is bonded through its α-amino nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
(the nitrogen bonded to the α-carbon) to a nucleobase
Nucleobase
Nucleobases are a group of nitrogen-based molecules that are required to form nucleotides, the basic building blocks of DNA and RNA. Nucleobases provide the molecular structure necessary for the hydrogen bonding of complementary DNA and RNA strands, and are key components in the formation of stable...
aglycone
Aglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...
by a C-N (carbon to nitrogen) bond. The new compound was determined to be toxic in the brine shrimp lethality test, but it did not have cytotoxic activity against a variety of human cancer cell lines
Cell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
. Other compounds isolated from the fungus include β-carboline
Beta-carboline
β-Carboline is an organic amine that is the prototype of a class of compounds known as β-carbolines.-Pharmacology:...
and russulaceramide (a ceramide
Ceramide
Ceramides are a family of lipid molecules. A ceramide is composed of sphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of cells. They are one of the component lipids that make up sphingomyelin, one of the major lipids in the lipid bilayer...
formerly found in some Russula
Russula
Around 750 worldwide species of mycorrhizal mushrooms compose the genus Russula. They are typically common, fairly large, and brightly colored - making them one of the most recognizable genera among mycologists and mushroom collectors...
mushrooms).