El sorprendente REINO FUNGI o de los hongos: características, nutrición, reproducción🍄

Key Concepts:

• Fungi kingdom: Eukaryotic, heterotrophic organisms with chitinous cell walls, including yeasts, molds, and mushrooms.
• Hyphae and mycelia: Filamentous structures forming the fungal body, responsible for nutrient absorption.
• Asexual reproduction: Fission, budding, fragmentation, and asexual spore formation (mitospores/meiospores).
• Sexual reproduction: Plasmogamy (cytoplasmic fusion), karyogamy (nuclear fusion), and meiosis.
• Heterotrophic nutrition: Saprophytes (decomposers), parasites, and symbionts (lichens, mycorrhizae).
• Phyla: Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, Microsporidia, Glomeromycota, Ascomycota, and Basidiomycota.

1. Overview of the Fungi Kingdom

• The Fungi kingdom is a large and diverse group of eukaryotic organisms, including yeasts, molds, and mushrooms.
• Estimated to contain over 1.5 million species, making it the second-largest kingdom after insects.
• Fungi constitute over 90% of terrestrial biomass when combined with prokaryotic and invertebrate organisms, making them the most abundant group in terms of soil biomass.
• Found in diverse environments, from Antarctic ice to tropical forests, and as parasites on plants, animals, and other organisms.

2. Characteristics of Fungi

• Eukaryotic: Fungi possess a nucleus and membrane-bound organelles, similar to animals and plants. Fungal cells are more similar to animal cells than plant cells in terms of internal organelles.
• Cell Wall: Fungi have cell walls made of chitin, a compound also found in insect exoskeletons, distinguishing them from plants with cellulose cell walls.
• Sessile and Multicellular: Most fungi are multicellular and sessile, meaning they are immobile and remain in a fixed location.
• Heterotrophic: Fungi are heterotrophic, obtaining nutrients from external sources, often decaying organic matter.
• Hyphae and Mycelia: Fungi grow via hyphae, filamentous structures that form a network called a mycelium, which absorbs nutrients. Hyphae are composed of cells in contact, allowing nutrient flow.

3. Classification of Fungi (Phyla)

• Fungi are a monophyletic group divided into 7 phyla:
  • Chytridiomycota: Saprophytic and parasitic, unicellular or filamentous, reproduce asexually via spores. Classes: Chytridiomycetes and Monoblepharidomycetes.
  • Blastocladiomycota: Parasites of plants and animals, some saprophytes, aquatic and terrestrial, alternation of generations. Class: Blastocladiomycetes.
  • Neocallimastigomycota: Anaerobic organisms in herbivore digestive tracts, produce asexual spores with flagella, have hydrogenosomes instead of mitochondria. Class: Neocallimastigomycetes.
  • Microsporidia: Parasitic fungi of animals and protists, phylogenetic relationships not fully elucidated.
  • Glomeromycota: Obligate mutualistic symbionts, associate with plant roots (mycorrhizae). Classes: Archaeosporomycetes, Glomeromycetes and Paraglomeromycetes and into four subphyla: Mucoromycotina Entomophthoromycotina Zoopagomycotina Kickxellomycotina
  • Ascomycota: "Sack fungi," symbionts in lichens, parasites or saprophytes, unicellular or filamentous, asexual reproduction via fission, budding, fragmentation, or spores, sexual reproduction via meiospores in asci within ascocarps. Subphyla: Taphrinomycotina, Saccharomycotina (yeasts), Pexixomycotina (lichen-forming fungi).
  • Basidiomycota: Produce uninucleate or dikaryotic mycelia, asexual reproduction via fragmentation or sporulation, sexual reproduction via hyphal fusion or fusion of reproductive structures, includes rusts, blights, mushrooms. Subphyla: Pucciniomycotina, Ustilaginomycotina, Agaricomycotina.

4. Reproduction in Fungi

• Fungi exhibit both asexual and sexual reproduction.
• Asexual Reproduction:
  • Fragmentation: New colonies form from hyphal fragments.
  • Budding: A "papilla" forms on a cell, enlarges, and separates as a clone.
  • Fission: A cell divides in half to form two new cells (e.g., in yeasts).
  • Asexual Spores: Formed by mitosis or meiosis, develop in elaborate structures.
• Sexual Reproduction:
  • Involves three sequential events: plasmogamy, karyogamy, and meiosis.
  • Plasmogamy: Fusion of protoplasts (plasma membrane and cytosol) containing compatible haploid nuclei.
  • Karyogamy: Fusion of haploid nuclei to form a diploid nucleus within a zygote.
  • Meiosis: Cell division that reduces the chromosome number, reestablishing the haploid phase and forming meiospores.
  • Compatible haploid nuclei are found through specialized sex cells (gametes) produced by gametangia or by fusion of vegetative hyphae.

5. Nutrition in Fungi

• Fungi are heterotrophic, unable to synthesize their own food from sunlight and CO2.
• Prefer carbohydrates as an energy and carbon source, and obtain nitrogen from protein breakdown.
• Can absorb and metabolize soluble carbohydrates (glucose, xylose, fructose, sucrose) and break down complex insoluble carbohydrates (cellulose, hemicellulose, lignin, starch) using digestive enzymes.
• Classified based on feeding method:
  • Saprophytes (Decomposers): Externally digest decaying organic matter and absorb nutrients.
  • Parasites: Obtain nutrients from host tissues, often harming the host.
  • Symbionts:
    • Lichens: Association with algae, where the alga is photosynthetic and the fungus is heterotrophic.
    • Mycorrhizae: Symbiotic relationship between plant roots and fungi, exchanging nutrients.

6. Synthesis/Conclusion

The Fungi kingdom is a vast and ecologically significant group of organisms characterized by their eukaryotic cellular structure, chitinous cell walls, heterotrophic nutrition, and unique reproductive strategies involving hyphae, mycelia, and both asexual and sexual spore formation. Their roles as decomposers, parasites, and symbionts are crucial for nutrient cycling and ecosystem health. The classification into different phyla reflects the diversity and evolutionary relationships within this kingdom.