The White Threads in Tempeh Are Hyphae
Fungi often appear as fine networks before a fruiting body is visible. The structure of those threads distinguishes fungal growth from plant roots and bacterial colonies.
A Mycelium Is a Network of Hyphae
In tempeh, a dense network of white hyphae from Rhizopus fungi binds the soybeans together. Those white threads are fungal hyphae. Many fungi build their bodies from hyphae that spread through food material. Unicellular fungi such as yeasts have a different body form.
Fungi are eukaryotic heterotrophs. Eukaryotic means their cells have a membrane-bound nucleus. Heterotrophic means they do not make their own food like chlorophyll-bearing plants. Fungi obtain nutrients by absorbing organic matter from living organisms or remains.
Fungi Absorb Nutrients from Organic Material
Fungi are heterotrophic eukaryotes characterized by structures such as hyphae, mycelium, and spores.
Fungi cannot photosynthesize. They obtain nutrients from organic material through an absorbing network of hyphae.
A fine branching network that absorbs nutrients from organic material may be fungal hyphae. Cell structure and other evidence are still needed to distinguish it from plant roots or another organism.
The hyphal network spreads across food material and expands the absorbing surface of the fungus.
- Part to observe
- Branching hyphae join into a mycelium that absorbs nutrients.
- Biological meaning
- Fungi digest outside the body, then absorb the breakdown products through the hyphal network.
| Fungal feature | Simple meaning | Function in the fungal body |
|---|---|---|
| Hyphae | Fine fungal threads | They give fungi a wide absorbing surface |
| Mycelium | A mass of hyphae | It lets the fungus spread through food, soil, or wood |
| External enzymes | Chemicals released outside the body | They break complex material before absorption |
| Chitin wall | A firm cell-wall material | It separates fungi from plants with cellulose walls |
Fungi Feed Differently from Animals
Fungi release enzymes onto organic material and absorb the smaller molecules produced by digestion. Animals usually digest food inside the body, while plants make sugars through photosynthesis.
Digestion Happens Outside the Body
Animals usually take food into the body and digest it inside. Fungi release enzymes into the environment, break complex organic material into smaller molecules, and then absorb the products.
This process is called extracellular digestion. Hyphae are fine threads that make up much of the fungal body and provide the contact surface for digestion and absorption. A mass of hyphae is called mycelium. As the mycelium spreads, a larger surface can contact the food.
Chitin Separates Fungal Walls from Plant Walls
Fungal cell walls contain chitin, while plant cell walls mainly contain cellulose. Chitin is also found in insect exoskeletons. Cell-wall material is one of the traits biologists use to distinguish fungi from plants.
Fungal Dispersal through Spores
Depending on the species and life-cycle stage, fungi can form spores sexually or asexually. Spores may disperse through air, water, animals, or contact with surfaces. Under suitable conditions, a viable spore can germinate and produce new hyphae.
Fungi grow easily on moist, nutrient-rich food when the temperature is suitable and viable spores or hyphal fragments are present.
A Fungal Role Depends on Its Environment
A fungus on a plant root may help the plant obtain water and minerals. A fungus on food may cause spoilage. Its effect depends on its environment and its relationship with nearby organisms.
Location and Relationships Determine a Fungal Role
Fungi can be helpful, harmful, or neutral depending on context. Yeast helps fermentation. Edible mushrooms become food. Soil fungi help decompose leaves and wood. But some fungi spoil food, attack crops, or cause disease.
Fungi occur in food, soil, roots, and infected tissue. Their effects change with the location, nutrient source, and nearby organisms.
Mycorrhizae between Fungi and Plant Roots
On plant roots, some fungi form mycorrhizae, relationships between fungi and roots. The fungi can support water and nutrient uptake, while the plant provides carbohydrates from photosynthesis. Fungal hyphae grow through the soil around the roots and increase the surface area available for water and mineral uptake.
Fungi Absorb Food after External Digestion
Animals take food into the body and digest it there. Fungi spread hyphae, break food down outside the body, and absorb the products. The white layer in tempeh is mycelium, an absorbing network that grows through organic material.
To identify a fungal role, ask three questions: where are the hyphae growing, what material is being broken down, and what relationship is forming with nearby organisms?