# Fungi

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Fungi are eukaryotic organisms closely related to animals. The study of fungi is known as mycology.

Some fungi are edible and could be grown for food in a Martian colony. Fungi, especially some sorts of mildew, are certainly of great use in the artificial ecosystem of a greenhouse, since they are involved in the decaying process.

Some people have an allergy against the spores of mildew, and patients with depressed immune system can suffer from a fungus infection. As yet, the development of the human immune system under Martian gravity and inhouse conditions is unclear.

## Cellular biology

### Cell wall

Fungal cells have cell walls which may be composed of several glucose polymers. For example, chitin (chains of acetylglucosamine joined by ${\displaystyle \beta (1\rightarrow 4)}$ links) or, as in yeast, callose (which is a glucose chain which differs from cellulose only in that it uses ${\displaystyle \beta (1\rightarrow 3)}$ links where cellulose uses ${\displaystyle \beta (1\rightarrow 4)}$ links[1].

### Cytoskeleton

Like all protozoa, animals and plants, fungi have cytoskeletal structures containing microtubules and microfilaments supporting the cytoplasm inside their cells[1]. In some fungi there are also intermediate filaments, though not to the same extent as in animals[1].
The microtubules can be thought of as analogous to the human skeleton, as they maintain the positions of major organelles within the cell[1] Furthermore, the microfilaments and microtubules are responsible for movement in eukarytic cells. This is achieved when the individual polymers slide across one another to create an overall lengthening or contraction of the structure[1].
It is worth noting that microgravity affects the cytoskeleton[2], so fungi could, in principle, be negatively affected by a journey to Mars. While the matter is of academic interest, fungi would almost certainly be much less harmed by a return to gravity than humans and no mission would therefore be compromised. It is even possible that fungi may grow more readily in microgravity, as some primitive eukaryotes do[2], though that is unlikely as the positive effect is at least mostly due to reduced energy expenditure during movement.

## Mushrooms

Mushrooms are the "fruiting bodies" of certain fungi or, more formally, the sporulating organs of certain complex fungi. The word toadstool is sometimes used in informal conversation to refer to inedible mushrooms. Mushrooms are complete proteins, and their nutritional value are in some respects (such as protein quality) in-between those of plant and animal foods. This makes them a potentially very valuable food source in spaceflight.

### Morphology

WIP: Explain the terminology used below.
Some mushrooms form inside a structure known as a "universal veil", a little bag which covers the entire mushroom and tears open as it grows. The universal veil is important in identification. Remnants of the base of the universal veil (known as the volval bag) are present in some species. Remnants of the top of the veil may remain as rough spots on the top of the cap, possibly a different colour (as in the culturally iconic white-spotted red mushroom, A. muscaria).

### Genus Amanita

Amanita spp. covers a number of edible mushrooms, as well as some of the most toxic known fungi. The Death Cap alone is responsible for more than 90% of mushroom-related deaths on Earth. Notable members of the genus include:

#### Amanita phalloides

Common name: Death Cap.
Deadly toxic to the liver and kidneys. (Lethal dose about 30g for adult humans[3].) Symptoms of poisoning include vomiting, diarrhoea, thirst and severe abdominal pain[3][4]. Symptoms will appear between 6 and 24 hours after ingestion[3]. If Amanita poisoning is not identified, the victim may appear to recover and die several days later from liver and/or kidney failure. Treatment includes carbon column dialysis, saline cathartic, repeated doses of activated charcoal and blood transfusions[3][4]. Fatal more often than not[3].
Identifying features[3][4]: Like all Amanitas, the Death Cap has a white spore print and forms inside a universal veil. The cap is smooth and flattens with age, growing to a maximum of about 15cm across. The ring is persistent, white and membranous. The gills are white, free and crowded. Pronounced volval bag. The flesh is white with a faint yellow tinge and the cap appears a slightly yellowish, greenish or smoky-olive white. A. phalloides var. alba is especially notable in that this rarer almost pure-white variety can be easily misidentified. The smell is described as "sickly sweet" to "foetid" and it is reported to have a pleasant taste.

#### Amanita citrina

Common name: False Death Cap.
To do.

#### Amanita pantherina

Common name: Panther Cap.
Highly toxic.
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#### Amanita rubescens

Common name: Blusher.
Edible when cooked. Toxic otherwise.
Description: To do.
Similar species: Non-experts may easily confuse A. rubescens with A. pantherina. To do: describe differences.

#### Amanita virosa

Common name: Destroying Angel.
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#### Amanita muscaria

Commonly known as Fly Amanita or Fly Agaric.
Edible if correctly prepared[5], despite the fact that field guides usually[3][4] (incorretly) list it as inedible. Detoxification involves boiling out the water-soluble toxins in water and either vinegar or salt, discarding the water[5]. If not detoxified, A. muscaria is hallucinogenic and causes euphoria similar to alcohol intoxification[4]. Relatively few fatalities have been recorded over several centuries and the lethal dose is not exactly known. The historical evidence collected by Rubel and Arora[5] suggests an adult lethal dose somewhere in the vicinity of 12-20 untreated mushrooms. Symptoms may persist for several days in the most extreme cases[4]
Trivia: A. muscaria was used for centuries to kill flies. After the crushed mushrooms have been mixed with milk, flies drinking the milk will become so intoxicated that they drown[3][5]. The Sami of Lapland sometimes scatter dried A. muscaria for their reindeer, as the intoxicating effect makes them easier to round up[4].

To do.

## References

1. S.L. Wolfe - Mollecular and cellular biology 1993. Wadsworth. ISBN 0-534-12408-9. pp. 17-18, 288-289, 514-517.
2. M.L. Lewis & M. Hughes-Fulford - Cellular responses to spaceflight 1997. (In S.E. Churchill, ed. - Fundamentals of space life sciences. Krieger. ISBN 0-89464-051-8) Vol 1. pp. 21-36.
3. M. Branch -- First field guide to mushrooms of Southern Africa 2001. Struik Nature. ISBN 978-1-86872-605-9. pp. 12-15.
4. P. Jordan -- The mushroom guide and identifier. 2010. Hermes House. ISBN 978-1-84038-574-8. pp. 100-113.
5. W. Rubel & D. Arora -- A study of cultural bias in field guide determinations of mushroom edibility using the iconic mushroom, Amanita muscaria, as an example. 2008. Economic Botany vol. 62 no. 3. pp. 223-243. Available here and here.