Kingdom Mycota or Fungi: General characteristics and classification

  • Kingdom Mycota consists of eukaryotic organisms.
  • Fungi exist in two fundamental forms; multicellular, filamentous or hyphal form (molds) and unicellular or budding form (yeast).
  • They lack chlorophyll (chloroplast) and can’t prepare their own food, hence are called organotrophic heterotrophs.
  • Most of them are saprophytic and some are parasitic.
  • They grow best in acidic environment tolerating acidic pH.
  • They can also tolerate high sugar concentration and dry condition.
  • Molds are obligate aerobes and yeasts are facultative anaerobes.
  • Optimum temperature of growth for most saprophytic fungi is 20-300C while 30-370C for parasitic fungi.
  • Fungi grow slowly as compared to bacteria.
  • Cell wall is composed of chitin.
  • Cell membrane consists of ergosterol.
  • Both asexual and sexual mode of reproduction occur
    • Asexual methods: fragmentation, somatic budding, fission, asexual spore formation
    • Sexual methods: gametic copulation, gamete-gametangium copulation, gametangium copulation, somatic copulation and spermatization.
  • More than 2,00,000 species of fungi are known, of which more than 100 fungi are responsible for human infection.
  • Some fungi show mutualistic relationship with higher plants, eg. Mycorrhiza is a symbiotic association with the roots of gymnosperms.

Classification of fungi:

  • Unlike that of bacteria, the classification of fungi is based primarily on the characteristics of the sexual spores and fruiting bodies present during the sexual stages of their life cycles.
  • However, the complete or perfect life cycles of many fungi are as yet unknown.
  • Based on the spore bearing structures, in which the spores are produced, fungi are classified into four divisions.
    • Ascomycota
    • Basidiomycota
    • Zygomycota
    • Deuteromycota
  1. Ascomycota (Sac fungi):
  • A sac like structure called ascus produces or bears sexual spores called ascospores.
  • Sexual reproduction occurs by single celled or multi-celled conidia.
  • Also known as sac fungi.
  • Hyphae are generally septate.
  • Examples: Saccharomyces, Arthroderma, Gibberella
  1. Basidiomycota (Club fungi):
  • Sexual spores called basidiospores are produced externally on a club shaped basidium.
  • Asexual reproduction occurs by budding, fragmentation or conidia formation
  • They are commonly called as mushroom group.
  • Hyphae are generally septate.
  • Examples: Amanita, Agaricus, Filobasidiella
  1. Zygomycota (Zygote forming fungi):
  • Sexual spore called Zygospore is formed by the fusion of two similar cells.
  • Asexual reproduction occurs by sporangiospore
  • Hypahe are generally aseptate.
  • Examples: Rhizopus, Mucor, Basidiobolus, Conidiobolus
  1. Deuteromycota (Imperfect fungi):
  • These fungi are also known as fungi imperfecti.
  • No sexual stage is present.
  • Asexual reproduction occurs by means of conidia.
  • They are pathogenic to most of the human beings and animals.
  • Examples: Candida, Cryptococcus, Trichophyton, Epidermophyton, Histoplasma

Importance of fungi:

  • Recycling: Since fungi are also decomposers, along with bacteria, they play a major role in recycling the dead and decayed matter.
  • Medicines: Penicillin antibiotic is derived from a common fungi Penicillium. Many other antibiotics like cephalosporin, griseofulvin etc. are also synthesized by fungi which are used to control diseases in humans and animals.
  • Food:
    • Many mushrooms are used as food by humans. Mushroom species are edible and are cultured in many parts of the world for sale.
    • Different types of food like kimchi, kinema, bakery products, brewery products are manufactured using fungi like Aspergillus, yeast etc.
  • Bio-control Agents: Fungi are used to parasitise or kill insects which help control pests. Spores of fungi are sprayed on crops, this method is cheaper and environment friendly.
  • Plant and Animal Diseases: Many fungi live on and in plants and animals causing diseases like blight disease in potato, rust disease in wheat, oral thrush and ringworm infection in humans etc.
  • Food spoilage: Fungal damage is responsible for large losses of stored food usually when the food contains moisture and sugar.

Kingdom Mycota or Fungi: General characteristics and classification