- 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
- 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
- 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
- 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
- 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.