Fungal mycelia

Microscopic view of a mycelium.  This image covers a one-millimeter square.

Another microscopic view of a mycelium.  Numbered ticks are 230 µm apart.

Oyster mushroom (Pleurotus ostreatus) growing on coffee grounds

Mycelia as seen under a log

Mycelium (plural mycelia) is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other substrates. A typical single spore germinates into a homokaryotic mycelium, which cannot reproduce sexually; when two compatible homokaryotic mycelia join and form a dikaryotic mycelium, that mycelium may form fruiting bodies such as mushrooms. A mycelium may be minute, forming a colony that is too small to see, or it may be extensive:

Is this the largest organism in the world? This 2,400-acre (9.7 km²) site in eastern Oregon had a contiguous growth of mycelium before logging roads cut through it.Estimated at 1,665 football fields in size and 2,200 years old, this one fungus has killed the forest above it several times over, and in so doing has built deeper soil layers that allow the growth of ever-larger stands of trees. Mushroom-forming forest fungi are unique in that their mycelial mats can achieve such massive proportions.

—Paul Stamets, Mycelium Running

It is through the mycelium that a fungus absorbs nutrients from its environment. It does this in a two-stage process. First, the hyphae secrete enzymes onto or into the food source, which break down biological polymers into smaller units such as monomers. These monomers are then absorbed into the mycelium by facilitated diffusion and active transport.

Mycelia are vital in terrestrial and aquatic ecosystems for their role in the decomposition of plant material. They contribute to the organic fraction of soil, and their growth releases carbon dioxide back into the atmosphere. The mycelium of mycorrhizal fungi increases the efficiency of water and nutrient absorption of most plants and confers resistance to some plant pathogens. Mycelia are an important food source for many soil invertebrates.

Sclerotia are compact or hard masses of mycelia.

Uses [edit]

One of the primary roles of fungi in an ecosystem is to decompose organic compounds. Petroleum products and pesticides, typical soil contaminants, are organic molecules, i.e. they are built on a carbon structure. This means that these substances present a potential carbon source for fungi. Hence, fungi have the potential to remove such pollutants from the soil environment, unless the chemicals prove toxic to the fungus. This biological degradation is a process known as bioremediation.

Mycelial mats have been suggested (see Paul Stamets) as having potential as biological filters, removing chemicals and microorganisms from soil and water. The use of fungal mycelia to accomplish this has been termed "mycofiltration".

Knowledge of the relationship between mycorrhizal fungi and plants suggests new ways to improve crop yields.

When spread on logging roads, mycelium can act as a binder, holding new soil in place and preventing washouts until woody plants can be established.

See also [edit]

• Carbon cycle

References [edit]

• Stamets, Paul. Mycelium Running, Ten Speed Press,U.S.A. 2005 (p. 45, caption to figure 60)

External links [edit]

• Mycofiltration: A novel approach for the bio-transformation of abandoned logging roads
• Paul Stamets: Six ways mushrooms can save the world
• The mycelium
• Eben Bayer's Talk about Greensulate at the TED conference