Kingdom fungi and its causes and its characteristics

  Kingdom Fungi

Fungi were regarded as plants because of the presence of certain characters since the last many decades, but detailed studies have revealed a set of characteristics that distinguish fungi from plants. Fungi lack chlorophyll, while the plants have this pigment; wall of a fungal cell is made up of a carbohydrate called chitin not found in plant cell walls; though generally filamentous, fungi are not truly multicellular like plants, because the cytoplasm of one fungal cell is continuous through pores with the cytoplasm of adjacent cells; and fungi are heterotrophic eukaryotes, while plants are autotrophic. It is mainly because of these reasons that fungi are placed in their own kingdom fungi. Fungi are generally saprophytes and are the most important decomposers in terrestrial ecosystem. Many fungi are also known as parasites of animals

and plants. They are found everywhere. They also develop symbiotic association with other organism. Recent finding are that fungi are more closely related to animals than plants. It is believed that fungi evolved from Fungi are heterotrophic unicellular flagellated ancestor. The ancestors of fungi and animals diverged into separate lineages about one billion years ago.

 General Characteristics of Fungi

Fungi are heterotrophic

 Fungi obtain their food by secreting digestive enzyme into substrates. Then they absorb the organic molecules released by the enzymatic action. 

Fungi have several cell types 

 Multicellular fungi are filamentous and the filaments are in the form of long slender structures called hyphae. Sometimes the filamentous form is lost and the hyphae are arranged in complex structures such as mushrooms.

Chitin cell wall 

The cell walls of fungi are made up of chitin, a nitrogen containing polysaccharide, which is more resistant to decompose than celluose

Nuclear mitosis 

Mitosis in fungi is different from that in plants and animals. The nuclear

envelope does not break and reform. Mitosis occurs in nucleus with nuclear membrane intact.

Classes of Fungi and their Diagnostic Features

Zygomycota

The members of the class are all terrestrial. They possess coenocytic hyphae. They live on decaying organic material. Zygomycota are characterized by the formation of sexual spores called zygospores formed by the mating hyphae. Both sexual and asexually produced sopores are Some members of the class are responsible for the rotting of bread,

peaches, strawberries and sweet potato during storage; other live as parasites or symbionts of animals, dispersed by air.

Rhizopus stolonifer, the common bread mold, is an important member of

zygomycota. The hyphae form a white or grey mycelium on bread. In asexual phase upright sporangiophores arise each of which bears a sporangium at its tip. Thousands of spores are formed in each sporangium.

The haploid spores are dispersed by air. Spores, when land on moist food, grow into new mycelia.

b. Ascomycota

The characteristic feature of ascomycota is the production of sexual are commonly called sac fungi. Unlike zygomycota, the most ascomycota spores called the ascospores within saclike asci (singular, ascus), thus, they bear their sexual states in fruit bodies called ascocarps which range in size from microscopic to macroscopic. Asci are produced in ascopcarps. Most of the ascomycota also reproduce asexually by means of conidia, produced in chains at the end of a conidiophores. causing powdery mildew. Certain members of the class are extremely Some of the ascomycota parasitize crops and ornamental plants beneficial. Many ascomycota are the decomposers of plant material. More than 40%live with green algae and cyanobacteria in beneficial association forming lichens. Some from mycorrihizea with roots of higher plants. Penicillin, the wonder drug, is obtained from a fungus called pencillium. Yeast is useful for both bakers and brewers. 

c. Basidiomycota

Basidiomycota not only include mushrooms, puffballs and shelf fungi but also important pathogen like rusts and smuts . They are also known as club fungi because of their club-shaped basidia. The mycelium in mycelium. Primary mycelium is also called monokaryon in which each cell

is unicucleate possessing a halploid nucleus, Secondary mycelium is basidiomycota exists in three forms i.e. primary, secondary and tertiary formed by an interaction with primary mycelium. It consists of dikaryotic cells in which each cell possesses two

haploid nuclei. When the mycelium becomes more complex and gives rise to fruit bodies (basidiocarps), it is called tertiary mycelium. Club-shaped basidia are arranged inside a fruit body called basidiocarp.

Karyogamy occurs in basidium which is followed by meiosis forming four haploid nuclei which are incorporated in basidiospores.

Sexual reproduction occurs through classical methods found in other

groups of fungi. Sexual reproduction in basidiomycota differs from all

other groups of fungi. No reproductive structures such as antheridia and

oogoina are formed. The sexual reproduction involves the conversion of

monokaryotoc phase to dikaryotic phase by various methods.

 Importance of Fungi

1.Fungi in pharmaceutical industry

Fungi have been used medicinally since ancient times. Ergotamine obtained from claviceps purpurea is used to facilitate delivery of babies and also used to relieve migraine headache. Pencillin, the first discovered antibiotic is produced by pencillium chrysogenum and other related

species. Cephalosporin is most widely used broad spectrum antibiotic, hair, nails, skin, athlete's foot and ringworm. obtained from cephalosporium acremonium and related species. Griseofulvin is an antibiotic used effectively against fungal infections of

It is obtained from a species of pencillium. Broad spectrum antibiotic cyclosporine used as a immunosuppressant drug in organ transplantation is also a fungal product.

2. Fungi in food industry

Yeast has been used by humans throughout recorded history.

Saccharomyces cerevisiae, (yeast) is used in baking and wine making

industry. It has got the ability to ferment carbohydrates, breaking down

glucose to produce ethanol and carbon dioxide. It is fundamental to the

production of bakery products, bear and wine.

3. Fungi used in research projects

Yeasts are mostly used in the biological research projects due to their

rapidly increasing generation time and increasing pool of genetic and biological information. It contains 6000 genes. In soft drink industry aspergillus sp. is used to produce citric acid for colas.

4. Edible fungi

Mushroom is considered popular food throughout the world. Mushroom pizzas are famous for their taste. The peculiar flavor and taste of certain types of cheese come from the fungi used in the processing, The

ascocarp of Morchella esculanta (a morel) and tuber melanosporum (a truffle) are highly prized for their complex flavor. Ectomycorrhizae of some plant families are also edible. Yeast is also used as a nutritional supplement because it contains high levels of B vitamins and about 50 percent of yeast is protein.

5. Symbiosis

Fungi develop many symbiotic associations with other organisins

lichens and mycorrhizac are the examples of this relationship.

a. Lichens

In a lichen, a fungus develops a symbiotic association with an algae in which alga is the photosynthetic partner. It is an excellent example of mutualism in which both the partners are benefited. Most of the visible body of the lichen consists of its fungal partner. Interspersed with the hyphae of

the fungus, there are found cyanobacteria, green algae or sometimes both. Specialized fungal hyphae penetrate the cell walls of algal partner and transfer nutrients directly to fungus. Biological signals sent out by fungus direct its algal partner to produce metabolic substances that it does not

produce when growing independent of fungus. Lichens are known as ioneers in ecological succession in extremely harsh habitats. Lichens are

often strikingly colored because of pigments that play a role in protecting

the photosynthetic partner from the destructive action of the sun's rays.

These pigments can be extracted from lichens and used as natural dyes.

b. Mycorrhizae

The roots of about 80% of all know species of vascular plants normally are involved in mutualistic symbiotic relationships with fungi. The association is called mycorrhizae. The fungus in a mycorrhiza

Increases total surface area of root system for soil contact and absorption. 

Mycorrhiza helps in the direct transfer of phosphorus, zinc, copper and other nutrients from the soil into the roots. The vascular plant supplies organic carbon to the fungus. There are two principal types of mycorrhizae. In endomycorrhizae, the

fungal hyphae penetrate the outer cells of the plant root, forming coils, swellings and minute branches and also extend out into the surrounding soil. In ectomycorrhizae, the hyphae surround but do not penetrate the cell walls of the roots.

6. Fungi as recycler

Fungi and bacteria are the principal decomposers in biosphere. Saprophytes exceed parasites in number in the ecosystem. They decompose the organic matter and release the substances locked in the dead bodies of plants and animals for circulation in the ecosystem. They possess a powerful enzyme system which helps in breaking down tough organic compounds

like lignin, a major constituent of wood. The substances thus released become available to the next generation of organisms. Fungi recycle the nutrients in nature and are called recyclers. The fungi clean the earth by

removing the organic matter and because of this characteristic they have earned the name scavenger.

7. Fungi as Food spoilers

Fungi also destroy food which is not properly preserved. It includes bread,

jams, cooked food etc. Fungi secrete substances into the food which make

the food unpalatable, carcinogenic and poisonous.

8.Pathogenic fungi

a.Plant diseases

Fungal diseases of plants are known to us since ancient times. Fungi are the serious agricultural pests. Most common fungal diseases of cereals are rusts and smuts caused by species of puccinia and

Ustilago respectively. Sometimes about 50 percent of world's fruit harvest is lost to fungal attack each year, Peach leaf curt, pear leaf spot and mildews are the diseases of fruits. Red rot of sugarcane, potato blight, late blight of tomato and many more diseases of plants are caused by fungi. 

b. Animal diseases

Ringworms in dogs and horses are caused by the species of Trichophyton and mircrosporum. Aspergillus sp. cause abortion in many animals Soprolegnia parasitica is the parasite of carp and salmon fish.

c. Diseases of humans

Almost all parts of human body are infected by fungi especially the skin. Rhizopus and Mucor species cause the infection of lungs, brain and gastric tissues. The cause of dandruff is Micosporum furfur. Candida sp.

cause throat and mouth diseases, pulmonary infection, diseases of nails and genital organs. Neurospora and Fusarium cause infection of corneal tissue of eye. Aspergillosis, whose symptoms resemble those oftuberculosis, is caused by Aspergillus sp. Athletet's foot is also a fungal

disease.