Question

Fungi symbioses with other organisms range from predation to mutualisms, and include benefits to humans, and disease predation parasitism commensalism mutualism human uses Mycoses (disease) Assign each example below to a category of relationship type in the table above. Also identify the type of organism that is in the relationship with the fungus, if it is not already noted. Saccaromyces cervisioe Ringworm Consumption of carbon compounds in industrial wastes Biofuel production Mycorrhizae (what are the 2 categories of this type? Decomposers (not a symbiosis per se, but still beneficial) Endophytes Leaf-cutter ants and fungal gardens Lichens Armillaria species in conifers Chytrids and amphibians aflatoxins Nematode-eating fungus Relationship with honeybees Antibiotics athlete's foot Cheeses yeast infections

Answer 1

Symbioses refers to the staying together of two or more organisms, that brings benefit to either one or both of them. Based on the advantage, there are four many types of symbioses:

1. Predation: Here, there is a symbioses between a predator and a prey, where the predator feeds on the prey. Thus, the predator has advantage while the prey doesn't.
2. Parasitism: The parasite survives on the host to obtain the food and/or nutrients. In the process, it weakens the host and might cause it to die. Thus, parasitism also involves advantage of just one partner, namely, the parasite.
3. Commensalism: Here, one of the members obtains benefits in terms of food or protection, while the other member is neutral.
4. Mutualism: This type of symbioses provides advantage to both the members.

Let us try to figure which category each of the examples belong to, alongwith, potential human use or damage, associated with each of these associations.

1. Mycorrhizae: These are the symbiotic associations between fungi and the plants. Here, the plants provide shelter and nutrition to the fungi. In return, the fungi provide nutrients to the plants, that they otherwise wouldn't be able to obtain. Since these increase the crop yield in farms, they are beneficial to humans. Based on the nature of the fungus, the mycorrhizae can be classified into:
   1. Ectomycorrhizae: The fungus is external to the plant.
   2. Endomycorrhizae: The fungus survives inside the plant.
2. Decomposers: Decomposers feed on the decaying organic matter thereby converting it into forms that can be used by other organisms for nutrients or food. They do not form a symbioses per se, but their interaction with all life forms on earth can be considered as mutualism. The life forms die and provide nutrition to the decomposers, which in turn, produce nutrients, minerals and gases, essential for the life forms to exist. They are hence beneficial to humans as well.
3. Endophytes: Endophytes refer to fungi that grow within a plant. They obtain protection, nourishment from the plants. In turn, they produce certain chemical compounds which prevent the grazing animals from feeding on these plants. Thus, they form a mutualistic interaction. Again by increasing crop yield, they are beneficial for humans.
4. Leaf-cutter ants and fungal gardens: Leaf-cutter ants are famous for their fungal farming. Within the ant-hills, they bring in fresh leaves and use these to farm fungus. This provides nutrition and growth for fungus. The fungus, in turn, acts as a food source for the ant larvae. Thus, this interaction is an instance of mutualism. This doesn't have any obvious direct effect on humans.
5. Lichens: Lichens are symbiotic associations of fungi and algae. The fungi grow alongside algae and obtain nourishment from the food synthesized by these algae. In return, they provide adherence, support to the algae. This is also an instance of mutualism. Lichens are beneficial to humans as they are used as food sources, for lichenification, as pH indicator, etc.
6. Armillaria species in conifers: Armillaria species are a very common fungi obtained in forest soils. These grow on trees that are barky and woody like conifers. They feed on wood and bark and renders the plant weak leading to wood decay and mortality. Thus, this is an instance of parasitism. These are harmful to humans as they can affect crop yield of woody plants and trees.
7. Chytrids and amphibians: Chytrid fungi feed on keratin. In larvae, the keratin is present mainly on the skin and around mouth parts. However, as they metamorphose into adults, the keratin is present at other areas too. Chytrid feeds on the keratin all over, causing a high rate of mortality of these amphibians. Thus, this is an instance of parasitism. It doesn't have any direct effect on humans.
8. Aflatoxins: Aflatoxins are toxins produced by fungi growing on plants to ward off harm. However, these toxins affect the plants causing mortality. It also affects the animals and humans that feed on the infected plants. Thus they are harmful to humans and are an instance of parasitism.
9. Cheeses: Cheese production involves fermenting of milk with fungi. The fungi fement the milk, thus providing them nutrition and growth. In turn, the fermented milk is used by humans to produce cheese, which is edible. Thus, this is an instance of mutualism between fungi and humans with cheese production being beneficial to humans.
10. Saccharomyces cervisiae: This fungal species, is probably, the most widely used fungi by humans. It has been used to brew beer and alcohols, ferment the dough to make bread, etc. It has also been used to study the genetics of eukaryotes and is one of the model organisms with genome sequenced. This is an instance of mutualism between humans and fungi.
11. Ringworm: Ringworm is caused by a fungus that feeds on keratin in humans. It produces bald patches of skin, often accompanied with rashes and inflammation. Since it causes diseases, it is an instance of parasitism. It is not beneficial to humans and causes disease.
12. Consumption of carbon compounds in industrial wastes: The fungi that feed on the carbon compounds that form industrial waste form a mutualistic relationship with humans and other life-forms. They feed on the carbon compounds and thus prevent them from seeping into water bodies and soil, thereby preventing toxicity. They are beneficial to humans.
13. Biofuel production: Certain fungi have been used to produce biofuel that can be used as a fuel for various reactors and engines. Thus, fungi that are benefited with food, nutrients and protection, provide humans with biofuel. This is an instance of mutualism.
14. Nematode-eating fungus: These fungi are carnivorous fungi, specialized at attacking and killing nematodes. They form a predatory relationship with the nematodes, where the nematodes are the prey. They help in maintaining the nematode population in garden soils, thereby preventing crop infestations. Thus, they are beneficial to humans.
15. Relationship with honeybees: Honeybees are cultured by humans to obtain honey. The honeybees get shelter and protection. In turn, the combs produced by them are used to obtain honey. Thus, this is an instance of mutualism. The humans are benefited from this relationship.
16. Antibiotics: Antibiotics are chemicals produced by certain fungi that prevent the growth of bacteria or kill them. Thus, this is an instance of predation. The fungi act as predators and kill their prey which are bacteria. This provides fungi with a space to grow without competition. These are beneficial to humans as the antibiotics can be used to kill harmful bacteria in the case of infections.
17. Athlete's foot: Athlete's foot is a fungal infection that starts mostly between the toes and occurs mostly with people who have sweaty feet. The fungi grow on skin and cause infection. Hence this is an instance of parasitism. They do not provide benefit to humans but rather cause disease.
18. Yeast infections: Yeast infections occur in areas that are moist like vaginal orifice, armpits, etc. The fungi get appropriate environment to survive and thrive while the human host is harmed due to infection and unhygienic fluid discharge. Thus, they form a parasitic relationship with humans thereby causing harm and disease.