Fungal Feeding Strategies

Chitin

A modified polysaccharide containing nitrogen that is the structural material making up the exoskeleton of fungi and arthropods.

Septum

Cross wall forming the division between two cells.

Hyphae

Extensions of a multicellular fungus; long thin tubes with or without septa.

ectomycorrhizal fungi

Fungal symbionts that grow outside the cell walls of plants.

arbuscular mycorrhizal fungi

Fungal symbionts that use haustoria to penetrate the cell walls of plants.

Describe structures and feeding mechanisms of fungi.

Fungi are heterotrophic organisms; they must find food rather than produce it. Fungi employ extracellular digestion to change their food sources into a form they can absorb. Many fungi use enzymes to digest large molecules, breaking them down into less complex compounds that the fungi then absorb.

Describe how different ecological niches provide fungi with multiple avenues for obtaining nutrients.

Fungi come in three main ecological groups (or niches): mutualists, parasites, and decomposers. When plant roots form a mutualistic symbiotic relationship with fungi in the soil, fungi receive photosynthetic products — carbohydrates — from the host plant and in return increase the area from which the plant can absorb mineral nutrients and water. In parasitic relationships, fungi secrete enzymes and absorb nutrients directly from the cells of their living host. When fungi act as decomposers, they secrete enzymes that allow them to absorb nutrients from organic material.

Mycelium

Large mass of hyphae composing multicellular fungi.

absorptive heterotrophy

Method used by fungi to obtain nutrients by the external breakdown of living organisms or organic material. The larger molecules are digested into smaller compounds, which are then absorbed by the fungal body. Some fungi use enzymes to break into living organisms' cells or tissues, and the fungus absorbs the internal nutrients.

Describe specialized forms of hyphae in fungi.

Multicellular fungi form filaments called hyphae to obtain nutrition. These hyphae form vast networks called mycelia. Fungal cell walls that surround the hyphae are composed of a strong, flexible nitrogen-containing polysaccharide called chitin. Most fungal hyphae nuclei are separated by septa. Aseptate hyphae lack septa. Haustoria are specialized hyphae that can either absorb nutrients from between cells of a host or penetrate the cell walls of living hosts and remove needed nutrients. Haustoria are seen in both mycorrhizal and parasitic fungi.

Yeast

Single-celled fungi.

Haustoria

Specialized hyphae of fungi used to extract or exchange nutrients.

Mycorrhiza

The symbiotic relationship between a fungus and the roots of a plant.

Explain the fundamental difference between fungi and plants in terms of capturing energy.

Though they may appear similar on the surface, plants and fungi obtain energy quite differently. Plants are autotrophs; they use energy from the sun to perform photosynthesis. Fungi are not photosynthetic; they must obtain energy from other organisms. They can do this by secreting enzymes to break down other organisms and absorb nutrients. Some fungi obtain nutrients through parasitic or mutualistic relationships with other organisms.