MYCELIUM: TYPES, CHARACTERISTICS, FUNCTIONS AND USES - BIOLOGY - 2025

Mycelium is the name given to the vegetative part of a fungus. These vegetative bodies are made up of multicellular filaments called hyphae, which resemble long threads, as they only grow apically.

These hyphae, and consequently the mycelium, can grow more than 1 mm per hour. Mycelium can grow in soil and on many other substrates. A mycelium can be tiny or very large.

Microscopic view of a mycelium. Photo by: Bob Blaylock - Own work, CC BY-SA 3.0. Taken and edited from commons.wikimedia.org

In eastern Oregon, a mycelium was found whose estimated extension was equivalent to 1,665 soccer fields and its age was estimated at about 2,200 years old.

The mycelia of filamentous fungi are made up of interconnected hyphae that grow apically and branch subapically. During the life cycle of a fungus, a spore will germinate in a homokaryotic mycelium.

Mycelia are made up of haploid hyphae. Some haploid hyphae can fuse in pairs to form binucleate haploid hyphae, called dikaryotes. These mycelia can form fruiting bodies.

Types

Vegetative mycelium

It is responsible for the absorption of nutrients, grows downward and penetrates the substrate to be degraded to fulfill its function. It has a high metabolism. Its hyphae are highly capable of osmotrophically absorbing dissolved substances in the medium.

This is done in two stages. Hyphae secrete enzymes on or into the food source. The function of these enzymes is to break down biological polymers into smaller units.

These units, called monomers, are taken up by the mycelium through facilitated diffusion and active transport.

Reproductive mycelium

This mycelium grows towards the external surface of the environment and is responsible for forming the reproductive structures (endosporites). It tends to be airy.

Its function is to support the development of spores. The reproductive mycelium develops in sectors where nutrients have been depleted. This allows the fungus that its spores can leave that place to colonize environments richer in nutrients.

Some characteristics of mycelia

Due to the growth form of hyphae, the periphery of the mycelium is formed by vegetative, young, rapidly growing hyphae with high metabolic activity.

Towards the center of the colony the mycelium is older. The environment where it grows is usually poor in nutrients. In this area the reproductive mycelium is more likely to develop.

Mycelial growth tends to be circular in shape due to branching and crossing of hyphae. This characteristic is indicative of the presence of fungi.

It can be observed in human skin lesions, plant leaves and fruit rots with such circular growth. The so-called witch rings are also proof of this type of growth.

Mycelia and plants

Arbuscular mycorrhizal fungi form symbiosis with approximately 80% of land plants. These fungi can grow on the inside or outside of the cortical cells of the plants they colonize.

The mycelium of the fungus acts as a complement to the root of the plant in taking nutrients. Additionally, the plant benefits by increasing the absorption of phosphorus and acquiring resistance to some pathogens.

Other benefits of the association are an increase in tolerance to abiotic stress conditions, an improvement in soil quality and an increase in nitrogen fixation.

Proof of this is the increase in the diversity and productivity of plants in environments where these fungi grow.

Sclerotia

Sclerotia are structures developed by some fungi that allow them to survive in extreme environmental periods. They are compact or hardened masses of mycelium. They contain food reserves.

In some species of fungi, the sclerotia shed and may remain dormant until environmental conditions are favorable for the development of a new mycelium.

Sclerotia in barley ear. Taken from commons.wikimedia.org

Importance of mycelia

Mycelium is of vital importance to terrestrial and aquatic ecosystems due to its role in the decomposition of plant material. Contributes to the organic fraction of the soil.

It favors nitrogen fixation in soils, and its growth releases carbon dioxide into the atmosphere. It also increases the productivity and resistance of plants, and is an important food source for many soil invertebrates.

Mycelium can act as a soil binder in forest crops during felling. It keeps the soil in place and prevents it from being washed out while new woody plants are established.

Applications

Bioremediation

One of the main functions of fungi in an ecosystem is to break down organic compounds. The mycelium of the fungus secretes extracellular enzymes and acids capable of breaking down lignin and cellulose.

These are organic compounds made up of long chains of carbon and hydrogen, structurally similar to many organic pollutants. Due to this, some fungi are capable of using petroleum products and some pesticides as a carbon source.

Therefore, they have the potential to eradicate these contaminants from the substrate where they develop. Some authors call this type of bioremediation microremediation.

Biofiltration

Mycelial mats have been suggested to have potential as biological filters. Mycelia function as membranes, filtering microorganisms and chemical and biological contaminants from the soil and water.

In addition, the mycelium reduces the flow of particles, mitigating erosion. The thin filaments of the mycelium not only trap contaminants, but often digest them as well. This type of biofiltration is also called micofiltration.

Bioplastics

The mycelium compounds are part of networks of filamentous hyphae. These use biological growth to convert low-cost organic waste into economically viable and environmentally friendly materials.

They are generally characterized as polymer grade foams and are used primarily for construction and packaging applications. However, a number of potential applications for these compounds have been proposed.

Potential applications include acoustic dampers, super absorbent polymers, paper, textiles, structural and electronic components.

Composting

Composting is a process of transformation of organic matter to obtain a natural fertilizer called compost. Fungi are essential to the composting process.

These organisms break down raw material compounds such as lignin, which many other composting microorganisms cannot. Composting can substantially decrease the amount of solid waste that goes to landfills.

References

1. M. Jones, T. Huynh, C. Dekiwadia, F. Daver, S. John (2017). Mycelium composites: a review of engineering characteristics and growth kinetics. Journal of Bionanoscience.
2. AA Meharg (2001). The potential for utilizing mycorrhizal associations in soils bioremediation. At GM Gadd. Fungi in Biorremediation. Cambridge University Press. United Kingdom.
3. Mycelium. On Wikipedia. Recovered from en.wikipedia.org
4. CJ Rhodes (2014). Mycoremediation (bioremediation with fungi) - growing mushrooms to clean the earth. Chemical Speciation and Bioavailability.
5. Sclerotium. On Wikipedia. Recovered from en.wikipedia.org.
6. P. Stamets (2005). Mycelium running. How mushrooms can help save the world. Have Speed ​​Press. New York.