Fungal Characteristics and Structure

Fungal Characteristics

• Fungi are heterotrophic, meaning they cannot produce their own food. They obtain carbon from other organisms.
• Heterotrophs—organisms that depend on other organisms for food—can be divided into different categories:
  • Parasites obtain nutrition from the protoplasm of another organism (the host). Some parasites cause disease and are called pathogens. They feed on the living tissue of the host.
  • Saprobes obtain carbon from nonliving organic matter. Often they consume the byproducts or remains of dead organisms. They are called decomposers. If environmental conditions change, some saprobes may become parasites and are called facultative parasites.

Fungal Structure & Form

• Eukaryotic: Fungi have membrane-bound organelles like the nucleus, mitochondria, endoplasmic reticulum, etc.
• Thallus: The vegetative body of a fungus can take different forms.
• Yeast: A unicellular form of fungus that reproduces asexually (by budding or fission).
• Mycelium (Molds): The collective strands or filaments of a fungus that make up the thallus.
  • Hyphae: The individual strands of a mycelium.
    • Septate: A hypha with cross-walls, called septa. The septa divide the hypha into discrete cells.
    • Coenocytic: A hypha without septa. The hyphae form a continuous structure and can have multiple nuclei within the one continuous tube.
• Dimorphic fungi: Some fungi exist in both mycelium and yeast forms.

Additional Fungal Characteristics

• Symbiosis: "Living together". Some fungi engage in a mutually beneficial relationship (mutualistic symbiosis)
  • Mycorrhizae: A mutually beneficial relationship between a fungus and roots of plants. The fungus helps the plant absorb water and nutrients, and the plant provides the fungus with carbohydrates.
  • Lichens: A mutualistic symbiotic relationship between a fungus and an alga or cyanobacterium. The alga or cyanobacterium provides food, and the fungus provides structure and protection.

Fungal Reproduction

• Spores: Fungi reproduce both sexually and asexually using spores.
  • Spores—sexual or asexual (mitotic or meiotic)—allow fungi to reproduce, spread to new food sources, and survive unfavorable conditions.
  • Spores are reproductive cells that can develop into a new fungal organism.
  • Fungi can form spores inside fruiting bodies or directly on hyphae.

Fungal Growth

• Mycelium and Hyphal growth: The feeding structure of a fungus, a network created by threads of hyphae.
• Mycelia: The mass of hyphae form a feeding network that allows fungi to absorb large amounts of nutrients.
• Hyphal tips: Where hyphae grow.

Other Characteristics of fungi

• Heterotrophic by Absorption: Fungi acquire nutrients from their surroundings by releasing enzymes, breaking down the organic matter, and then absorbing the digested products.
• Cell Wall: Fungi have a cell wall composed of chitin.
• Food Storage: Fungi store food in the form of glycogen and lipids.
• Habitat: Fungi grow in almost every habitat on earth in which organic matter exists.
• Diversity: Fungi exhibit a great diversity in form, structure, and function. The estimated number of species ranges from 69,000-100,000, possibly reaching over 1.5 million.