Fungal threads may make up a quarter of soil’s living mass
Mycelium is the hidden body of a fungus: a tangle of branching threads that digests food outside itself and then absorbs the pieces. These networks may account for 20 to 30 percent of soil biomass, link most plants’ roots, and are now being grown into packaging, leather substitutes and building blocks.
A fungus feeds in two steps. Its hyphae release enzymes that break large biological molecules into small units such as monomers, which the mycelium then takes in by facilitated diffusion and active transport. A single germinating spore produces mycelium that cannot reproduce sexually; only when two compatible strands fuse can the combined network form fruiting bodies. Hardened masses of mycelium are called sclerotia, and the networks can carry water and spikes of electrical potential.
In ecosystems mycelium breaks down plant material, builds up the organic part of soil and returns carbon dioxide to the air. Mycorrhizal mycelium helps most plants take up water and nutrients and resist some diseases. About 83 percent of plants appear to partner with it as an extension of their roots, and by some estimates the fungi receive more than a tenth of their hosts’ photosynthetic output. Fungi also digest lignin, which many other compost microbes cannot, and could clear petroleum and some pesticides from soil, a practice called mycoremediation; mats of mycelium have been proposed as filters for water and soil.
Grown on agricultural waste or sawdust, mycelium can replace polystyrene packaging and be pressed into artificial leather, though adding polyester or polylactic acid can spoil its biodegradability. As a building material it is light, insulating, sound-absorbing and low in embodied energy, and it takes the shape of any mould. Its weakness is compression: it withstands only 0.1 to 0.2 MPa, against 17 to 28 MPa for ordinary concrete, and as a living material it can be contaminated during growth. Builders grow it as moulded blocks, as monolithic structures in place, or as bio-welded units, and life-cycle studies suggest it can act as a carbon sink.
Source: Mycelium
