Hypha

A hypha is a microscopic, tube-shaped filament that forms the main body of a mold or a mushroom-forming fungus. Each hypha is enclosed in a chitin cell wall and filled with cytoplasm, and it grows at its tip, branching as it spreads through soil, wood or food. A tangled network of hyphae is called a mycelium. Even a mushroom is made of hyphae, packed tightly together.

Hyphae come in two main forms. Septate hyphae are divided into cell-like compartments by cross walls called septa, which usually have pores that let cytoplasm, and sometimes nuclei, flow from one compartment to the next. Coenocytic hyphae, found in bread molds, have no septa, so each one is a long continuous cell containing many nuclei. Because hyphae are thin and branch widely, they give a fungus a huge surface for releasing digestive enzymes and absorbing the food they free.

In the microbiology lab, whether hyphae have septa, and how they branch and carry spores, helps identify molds under the microscope. Some yeasts form chains of elongated buds called pseudohyphae, which look similar but are not true hyphae.