Fungi: morphology, classification, reproduction & cultivation

• The study of fungi encompasses various aspects, including their morphology, classification, reproduction/replication, and cultivation.

Morphology of Fungi

Structure:

1. Hyphae: The basic structural units of fungus, which are long, thread-like filaments. They can be septate (divided by cross walls) or coenocytic (without septa).
2. Mycelium: A network of hyphae that forms the body (thallus) of the fungus. The mycelium is responsible for nutrient absorption.
3. Spores: Reproductive units that can be asexual (conidia, sporangiospores) or sexual (ascospores, basidiospores).
4. Fruiting Bodies: Specialized structures like mushrooms, which produce and release spores.

Cellular Organization:

1. Cell Wall: Composed mainly of chitin, glucans, and sometimes cellulose.
2. Cell Membrane: Contains ergosterol, different from cholesterol found in animal cells.
3. Organelles: Includes a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and sometimes vacuoles.

Classification of Fungi:

Kingdom Fungi:

• Fungi are classified based on their reproductive structures and methods, molecular data, and other morphological features.

Major Phyla:

1. Zygomycota (Zygomycetes): Known for zygospores formed during sexual reproduction. Example: Rhizopus (bread mold).
2. Ascomycota (Sac Fungi): Produce spores in sac-like structures called asci. Includes yeasts and molds. Example: Saccharomyces cerevisiae (baker’s yeast).
3. Basidiomycota (Club Fungi): Produce spores on club-shaped structures called basidia. Includes mushrooms and toadstools. Example: Agaricus bisporus (common mushroom).
4. Deuteromycota (Imperfect Fungi): For this only asexual reproduction is known (e.g., Penicillium).

Fungal Forms:

1. Yeasts: Unicellular fungus that reproduce by budding or fission.
2. Molds: Multicellular fungus with filamentous hyphae.

Reproduction/Replication of Fungi

1. Asexual Reproduction:

   • Budding: Common in yeasts, where a new cell grows out of the body of a parent.
   • Fission: Simple cell division in unicellular fungus.
   • Spore Formation: Asexual spores (conidia, sporangiospores) are produced by mitosis and dispersed to form new individuals.

2. Sexual Reproduction:

   • Plasmogamy: Fusion of cytoplasm from two parent mycelia.
   • Karyogamy: Fusion of nuclei from two parent mycelia.
   • Meiosis: Reductional division to produce sexual spores (ascospores, basidiospores).
   • Spore Dispersal: Spores are released into the environment to germinate into new mycelia.

Cultivation of Fungi

1. Environmental Conditions:

   • Temperature: Most fungi grow well at 20-30°C, though some can tolerate extremes.
   • pH: Optimal pH for most fungus is slightly acidic (pH 4-6).
   • Moisture: High humidity is generally favorable for fungal growth.
   • Nutrients: Fungus require organic matter, nitrogen, vitamins, and minerals.

2. Culture Media:

   • Potato Dextrose Agar (PDA): Common medium for general cultivation.
   • Sabouraud Dextrose Agar (SDA): Used for fungi with acidic tolerance.
   • Malt Extract Agar (MEA): Rich in nutrients for fastidious fungus.

3. Techniques:

   • Inoculation: Introducing fungal spores or mycelium to the culture medium.
   • Incubation: Maintaining the culture under suitable environmental conditions.
   • Isolation: Obtaining pure cultures by subculturing from a mixed population

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