Fungi - Overview, Characters, Classification, Examples, Importance

Overview.

• Alexander Flemming stated the importance of Penicillium notatum while he was working on bacteria Staphylococcus.

• According to  Alexopoulos Fungi are nucleated with non chlorophyll bearing organisms, which  reproduce by both  asexually and sexually and their cell walls are made up of chitin.

• The study of fungi is called Mycology.

General account of Fungi-

• Fungi can be seen in moist bread and rotten juices. Mushroom are edible fungi. Toad stool grow on dung is also fungi.

• Unicellular fungi like yeast is used in production of wine and beer. Some multicellular fungi like penicillium is used in formation of Antibiotics.

• White spot on mustard and Rust and Smut disease in plant are also caused by the fungi.

• They are saprophytic in nature because they grow on dead matter of  plants and animals and collect their food from these matter.

• Fungi need warm and humid condition to grow.

• Body of fungi is composed of long thread like structure called hyphae. The network of hyphae is called mycelium. The hyphae is coenocytic with multinucleated or septate.

• They cannot make their own food due to lack of chlorophyll. They also act as Biofertilizer.

Know about the Microbes used as Biofertilizer

Reproduction in Fungi :

• Fungi  reproduce by Vegetative reproduction,  Asexual reproduction and Sexual reproduction.

• They reproduce vegetatively by budding, fragmentation, fission.
• Fungi reproduce asexually by  special structure like rhizomorph and sclerotia.

• Conidia, chlamydospore, endospores, basidiospore, uredospore, ascospores, pycniospores, teleutospore are spores in fungi that are formed in favourable condition.

• Sexual reproduction in fungi may be  isogamous, anisogamous and oogamous.

Dikaryophase

• In unfavourable condition, two same type of hyphae are come together and fuse through conjugation tube.

• Their protoplasm are fused through conjugation tube and make a single cell by the process of plasmogamy.

• At this stage, there are two nucleus in a cell therefore this stage is called Dikaryophase and nuclei are called dikaryon.

• Dikaryophase stage is frequently seen in member of Ascomycetes and Basidiomycetes.

• Now both nuclei are fused to each other through the karyogamy and form a diploid zygote.

• This zygote divides by meiosis and form many spores in fruiting bodies.

Know about the Kingdom Monera

General characteristics of Fungi:

• They are almost cosmopolitan in nature and found in soil, water, air and even in plants and animal bodies.

• They have a filamentous and thallus-like body structure except yeast.

• They are devoid of chlorophyll therefore they are not green in color.Due to lack of chlorophyll, they do not perform photosynthesis.

• They exhibit a heterotrophic mode of nutrition, thus they are not capable of making their own food. They are completely dependent on other organisms for their  nutrition as Parasites and saprophytes.

• They are saprotrophic  because they derive nutrition from the dead and decaying matter.

• Their cell wall is mainly composed of chitin, a kind of polysaccharides. Along with the chitin, the cell wall of some fungi also have cellulose.

• Some fungi prefer be  to live in darkness or in the absence of light hence they are  photophobic and some may live in the presence of light called photophilic

• Body of fungi is composed of a network of thread-like structures called mycelium. The  mass of mycelium forms specific fungal tissue called pseudoparenchyma.

• Fungi store reserve food material in the form of glycogen.

• Some fungi make symbiotic association with algae and root of higher plants known as lichen and mycorrhiza respectively.

Classification of fungi:

• Fungi are classified into four major groups on the basis of Morphology of mycelium, formation of spores and formation of fruiting bodies.

Phycomycetes:

• Members of this group are found in moist, damp places, dead and decaying matter.

• Their mycelium is coenocytic with many nuclei. Their network of  mycelium  is well developed.

• They reproduce asexually  by motile and nonmotile spores called zoospores and aplanospores respectively.
• They reproduce sexually by Zygospore that are formed by fusion of the protoplasts of two gametes. 

• During fusion of gamete, a conjugation tube is formed to make the fusion of protoplast between the two cells of fungi.Therefore they are also  called conjugation fungi.

• When both  gametes are morphologically  similar that are involved in sexual reproduction, then reproduction is isogamous.

• In anisogamous or oogamous , both gametes are not morphologically similar. 

• They have some affinities with the algae therefore called as Algal fungi.

• Example: 1. Rhizopus or  Bread Mould 2 .Mucor. 3. Albugo, Parasite on Mustard.

Ascomycetes:

• They are also called sac fungi and are regarded as higher fungi.

• It is the largest group of fungi including 1700 genus  and 15000 species.

• They are saprotrophs , decomposers and parasites.  They are also coprophilous because they may grow on cow dung.

• Their mycelium is branched and septate.

• They reproduce asexually by the conidia. These conidia are produced exogenously on special mycelium called conidiophore.

• They reproduce sexually by the specialised sexual spores called ascospores. Ascospores are formed  endogenously usually eight in numbers and present within a  sac-like structure  called ascus.  Therefore they are called ascomycetes.

• They are mostly multicellular like penicillium  but some are unicellular like Saccharomyces.
• For example- Aspergillus, Claviceps, Neurospora. Fusarium.

👌👌Remember- Neurospora is widely used in biochemical and genetic experiments. 

Basidiomycetes:

• The members  are commonly called mushroom or bracket fungi or puffball.

• They are found in soil or damp trees or moist places.

• They may also be present in the plant body as parasites in the form of smut and rust.

• Their mycelium is branched and septate.

• Asexual mode of reproduction is unknown but they reproduce in vegetable mode  by fragmentaion.

• They do not have any sex organs but they reproduce sexually by fusion of protoplast between two different cells by plasmogamy  and form a club-shaped structure  called the basidium. Hence they are also referred to as club fungi.

• Inside the basidium, by meiosis basidiospores are formed. These  basidiospores are arranged in  the fruiting bodies  called basidiocarps. 
• Example: 1. Agaricus or Mushroom 2. Ustilago causes smut disease  3. Puccinia causes rust disease. 

Deuteromycetes:

• They are also called imperfect fungi because the sexual stage is not known in members of this group.

• They reproduces by asexual means mainly through conidia like Ascomycetes.

• They were grouped initially in ascomycetes but due to absence of sexual stage.

• They have been placed in different group.They are pathogenic and cause harmful diseases in humans and animals.

• Their mycelium is branched and septate.

• They are saprotrophs or parasite .They are also involved in mineral cycling in nature. Example:  Alternaria, Colletotrichum, Trichoderma.

Multiple Choice Questions on Fungi

Commercial use of Fungi 

Mushroom

• At  industrial scale, mushrooms are cultivated from fungi.

• Mushrooms have high nutritional value.

• Mushrooms are rich in vitamin B. It is  regarded as a source of protein.

Yeast

• Yeasts are used in the bread making industry. 

• Yeast is also used in the production of wine whisky rum  industries because yeast produces  ethyl alcohol by fermentation.

Know about Microbes used in commercial Product

Penicillium

• Penicillium is enriched in protein,  vitamin A, vitamin B.

• It is added to increase the flavour to the cheese. 

• Penicillin was the first antibiotics that was discovered from Penicillium nnotatum

Know about the Microbes used in formation of antibiotics

• Aspergillus produces citric acid, Gallic acid which is used in the chemical industry.  .

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