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Hypha

life science Maturity 9-11 Next article →

A hypha is a long, branching, and filamentous structure. These structures belong to fungi, oomycetes, or actinobacteria. In most fungi, hyphae serve as the primary mode of vegetative growth. When many hyphae grow together in a mass, they are called a mycelium.

HYPHAE
HYPHAE

Most hyphae have an average diameter of 4 to 6 micrometers. They consist of one or more cells surrounded by a tubular cell wall. In fungi, this wall is typically made of a structural polymer called chitin. This differs from plants and oomycetes, which use cellulose for their cell walls.

Hyphae grow specifically at their tips through a process called apical growth. This growth occurs as the cell extends its walls through the external assembly of new components. Inside the cell, the membrane is also being produced. A key organelle in this process is the Spitzenkörper, a German term meaning "pointed body."

Conidium
Conidium

The Spitzenkörper is part of the endomembrane system. It acts as a collection point for membrane-bound vesicles received from the Golgi apparatus. These vesicles travel to the cell membrane using the cytoskeleton. Through exocytosis, the vesicles release their contents outside the cell. These contents include various cysteine-rich proteins, such as hydrophobins and cerato-platanins. The vesicle membranes help grow the cell membrane, while the contents form the new cell wall. The movement of the Spitzenkörper along the apex regulates the rate of growth and branching.

Hyphae can be classified by how their cells are divided. Most fungi have septate hyphae, which means they are partitioned by internal cross-walls called septa.

Penicillium
Penicillium

These septa are usually perforated by pores. These pores allow ribosomes, mitochondria, and sometimes nuclei to flow between cells. However, some fungi possess aseptate hyphae. These are also called coenocytic hyphae because they lack these internal partitions. For example, the fungus Mucor has non-septate hyphae. Yeast can also form pseudohyphae. These are not true hyphae because they grow through an incomplete budding process. In pseudohyphae, cells elongate but remain attached after division, lacking cytoplasmic connections.

Hyphae are highly adaptable and can modify their shapes for specific functions. Some parasitic fungi develop haustoria, which are specialized structures used for absorption within a host's cells. In mutualistic relationships, mycorrhizal fungi use arbuscules to exchange nutrients with plants.

Aspergillus niger 01
Aspergillus niger 01

These arbuscules help plants absorb water and nutrients. Ectomycorrhizal fungi create an extramatrical mycelium that increases the soil area available to plant hosts. In lichens, hyphae envelop the gonidia to form much of the lichen's structure. Some fungi even use hyphae to hunt. Nematode-trapping fungi can grow hyphae into constricting rings or adhesive nets to catch tiny worms. Other hyphae form mycelial cords to move nutrients over long distances.

In the study of basidiomycetes, hyphae are categorized by their physical characteristics. There are three main types: generative, skeletal, and binding hyphae. Generative hyphae are relatively undifferentiated and can develop into reproductive structures. They are typically thin-walled and often have frequent septa. Skeletal hyphae are much longer and have very thick walls. They are often unbranched and have few septa. There is also a version called fusiform skeletal hyphae, which are swollen in the center and very broad. Binding hyphae are also thick-walled but are frequently branched. They can resemble the shape of deer antlers or defoliated trees.

In 1932, a researcher named E. J. H. Corner created a system to classify these hyphal structures. He used the types of hyphae to describe the systems in polypores. If a fungus contains only generative hyphae, it is called monomitic. Fleshy mushrooms, such as agarics, are monomitic. If a fungus has generative hyphae plus either skeletal or binding hyphae, it is dimitic. Most dimitic fungi combine generative and skeletal hyphae. In 1966, Corner refined these terms further. A fungus with all three types is called trimitic. This complexity gives leathery or woody fungi, like polypores, their tough texture. Some specialized systems are called sarcodimitic or sarcotrimitic depending on the specific combination of these hyphal types.

Hyphae also show complex behaviors in response to their surroundings. They can sense reproductive units from a distance and grow toward them. They can also sense and respond to environmental stimuli, such as an electric field.

Hypha on rice
Hypha on rice

Furthermore, hyphae are capable of weaving through permeable surfaces to penetrate them. They can be categorized by where they grow, such as vegetative hyphae or aerial hyphae. Aerial hyphae are important because they produce asexual reproductive spores. This ability to grow and respond allows fungi to interact deeply with their entire ecosystem.

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🖼️ Images & Media (5)
File:Penicillium.jpg
Penicillium.jpg
File:HYPHAE.png
HYPHAE.png
File:Hypha on rice.jpg
Hypha on rice.jpg
File:Aspergillus niger 01.jpg
Aspergillus niger 01.jpg
File:Conidium.png
Conidium.png
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