Fungi: characteristics and classification
Characteristics of Fungi
1. Fungi is a separate kingdom
2. Fungi are Eukaryotic organism
3. Morphology:
- Fungi exists in two fundamental forms, filamentous or hyphal form (MOLD) and singe celled or budding form (YEAST).
- But for the classification of fungi, they are studied as mold, yeast, yeast like fungi and dimorphic fungi.
- Yeast is Unicellular while Mold is multicellular and filamentous
4. Fungi lacks Chloroplast.
5. Mode of nutrition:
- Fungi are organotropic heterotrophs.
- Mostly Fungi are saprophytic and some are Parasitic
6. Fungi grow best in acidic environment ( tolerate acidic pH).
7. Fungi can tolerate high sugar concentration and dry condition
8. Most of the fungi are Obligate aerobes (molds) and few are facultative anaerobes (yeasts)
9. Optimum temperature of growth for most saprophytic fungi is 20-30 C while (30-37) C for parasitic fungi.
10. Growth rate of fungi is slower than that of bacteria.
11. Cell wall is composed of chitin
12. Cell membrane consists of ergosterol
13. Reproduction: both asexual (Axamorph) and sexual (Teliomorph) mode of reproduction
- Asexual methods: fragmentation, fsomatic budding, fission, asexual spore formation
- Sexual methods: gametic copulation, gamate-gametangium opulation, gametangium copulation, somatic copulation and Spermatization.
14. More than 2,00,000 fungi species are known.
15. More than 100 fungi are responsible for human infection.
16. More than 20 species are responsible to cause severe systemic human infection, 35 species causes less severe systemic disease or might causes cutaneous or sub cutaneous infection and 45 species causes superficial cutaneous infection.
17. Some fungi shows mutualistic relationship with higher plants, eg Mycorrhiza is symbiotic associated with root of gymnosperm
Classification of fungi:
The kingdom fungi or mycota is classified into 9 division however only four division are involved in medical mycology
1. Ascomycetes
2. Basidiomycetes
3. Zygomycetes
4. Deuteromycetes
Ascomycetes:
- Sexual spore produced within a sac like structure called ascus.
- Sexual spore are called ascospore
- Asexual reproduction occurs by single celled or multi celled conidia
- Ascomycetes are also known as sac mycetes.
- Hyphae are generally septated
- Examples: Saccharomyces, Arthroderma, Gibberella
Basidiomycetes:
- Sexual spore are produced externally on a basidium
- Sexual spore are known as basidiospore
- Asexual reproduction occurs by budding, fragmentation or conidia formation
- They are commonly called as mushroom group
- Hyphae are generally septated
- Examples: Amanita, Agaricus, Filobasidiella
Zygomycetes:
- Sexual spore are known as Zygospore
- Zygospore is formed by fusion of two similar cell.
- Asexual reproduction occurs by sporangiospore
- Hypahe are generally aseptated.
- Examples: Rhizopus, Mucor, Basidiobolus, Conidiobolus
Deuteromycetes:
- No sexual stage is present
- Deuteromycetes are also known as fungi imperfecti.
- Asexual reproduction occurs by means of conidia.
- Most of the human and animal pathogens are present in this class.
- Examples: Candida, Cryptococcus, Trichophyton, Epidermophyton, Histoplasma
Importance of fungi:
i. Important agents for biodegradation and bio-deterioration
ii. Use in industrial fermentation process.
- Examples; Penicillium notatum is used for production of penicillin antibiotics
- Aspergillus niger is used for prodution of citric acid
- Saccharomyces cerevisiae is used for alcohol production
iii. Used in bioremediation (reduces toxic concentration)
iv. Used in agriculture, horticulture and forestry, example; biofertilizer and biopesticides