The fungi kingdom contains eukaryotic organisms such as mushrooms, molds, mildews, and yeasts. Fungi differentiate themselves from other eukaryotes like plant and animals by having chitin in their cell walls. It is estimated that there are 2.2 million to 3.8 million species of fungi but only about 120,000 have been identified and described. Fungi play an important role in nature as the principal decomposers in ecosystems. Structurally, the hyphae and mycelium are the two main components of fungi.

The Hyphae

Hyphae are the masses of branched, tubular, thread-like filaments about 4-6 micrometers in diameter that penetrate into substrates and absorb nutrients. They secrete enzymes that break down nutrients into smaller molecules before being absorbed. Masses of hyphae are sometimes called a shiro. When hyphae come together and fuse, they form a mycelium. Hyphae grow at the tip with the help of an organelle called the spitzenkörper (German, meaning pointed body). Sometimes hyphae create individual cells by forming walls called septa. New hyphae come from spores on the mycelia.

Fungal hyphae mass
The image above shows the masses of thread-like filaments that make up hyphae.

The Mycelium

Hyphae branch into a complicated and expanding patchwork called a mycelium which forms the thallus, or vegetative part of the fungus. This part can be microscopic or visible as mushrooms, toadstools, puffballs, and truffles. Spores are formed on the mycelium which develop and grow into hyphae. Only dikaryotic (those with 2 nuclei) mycelium are capable of sexual reproduction while homokaryotic mycelium reproduce asexually. In addition, multi-cellular fungi are classified based on the structure of their mycelium.

Mycelium growing on coffee grounds
The image above shows the patchwork appearance of the mycelium in the oyster mushroom Pleurotus ostreatus.

Comparison Table

Hyphae Mycelium
The vegetative part of a fungus No Yes
The filamentous part of a fungus Yes No
Produces spores No Yes
Main area of growth on a fungus Yes, at the tips No
Present in yeast? Yes No, individual cells
Also called shiro Yes No
Are thread-like in appearance Yes No
Has an organelle called the spitzenkörper Yes No

References

  • Fungus. (n.d.). In Wikipedia. Retrieved April 18, 2018 from https://en.wikipedia.org/wiki/Fungus
  • Alexopoulos, C.J., Moore, D. & Ahmadjian, V. (2018). Fungus. In Encyclopedia Britannica. Retrieved from https://www.britannica.com/science/fungus