Kingdom Fungi- Structure, Characteristics, Classification, Classifications, Concepts

What Is Fungi?

Systematics of fungi is a vast group of eukaryotic microbes that are fundamental to all other organism groups and human civilisation. They perform important functions as the recyclers of matter and nutrients in the terrestrial and aquatic systems. Further, the fungi also become mutualistic partners of plants by helping in the acquisition of nutrients and increasing the plant’s ability to withstand stress.

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The use and classification of fungi started with early naturalists and taxonomists; it progressed from those associated with plants to the modern and more scientific basis of morphology and genetics. That is why it is critical to know about their ecological significance and context to comprehend their value to nature, farming, pharmaceuticals, and bioengineering in today’s world.

Cell Structure Of Fungi

Fungi possess unique cellular features that distinguish them within the biological kingdom:

Eukaryotic cells

• Fungal cells are well-developed eukaryotic cells containing a well-defined nucleus with hereditary material in the form of DNA surrounded by the nuclear membrane.

• It depicts the fungi as different from prokaryotic organisms such as bacteria.

Cell Wall Composition (Chitin)

• Unlike plant cells which have both a cell wall and a cell membrane, fungal cells have only the cell wall, mostly made up of chitin a polymer of N-acetyl glucosamine.

• It gives rigidity and a mechanical shield against various forces, similar to cellulose offering plants the corresponding purpose.

• This composition stands out among other members of eukaryotes and helps diverse fungi adapt to numerous conditions.

Characteristics Of Fungi

Fungi exhibit diverse nutritional strategies that contribute to their ecological roles:

Nutrition

Saprophytic:

• Some fungi are parasitic while most of the fungi are saprophytic, thus breaking down dead organic matter and returning nutrients to the ecosystems.

• Thus, they are involved in nutrient cycling and improving the fertility of the soil.

Parasitic:

• Of the types of fungi, there are parasitic fungi, these fungi derive their nutrients from living organisms.

• These pathogens are capable of causing diseases in plants, animals and humans with consequences in agriculture, silviculture, and medicine.

Mutualistic:

• Some fungi interact with plants and other organisms in mutualistic ways; such as mycorrhizal fungi.

• The mycorrhizal fungi improve plant nutrient acquisition while the endophytic fungi have benefits such as; the ability to improve plant stress tolerance.

Reproduction

Fungi reproduce asexually through mechanisms such as:

Asexual Reproduction

Spores:

• Heterosporous plants reproduce by asexual spores which are formed as a result of mitosis and reproduce through the help of wind, water or animals.

• They develop into new fungal growth if they are exposed to favourable conditions.

Budding:

• Yeast reproduces asexually and the kind of reproduction that operates at this level is through budding.

• This is a process whereby the parent cell grows a small projection or bud, which later forms an individual cell.

Sexual Reproduction

Fungi also undergo sexual reproduction, involving:

Spore formation:

• Sexual spores are formed as a result of a gametes fusion and new environments are colonised.

• This process contributes to the genetical variation of the fungi species.

Mating types:

• Mating types in fungi are plus and minus and dictate the compatibility of the two types in the process of sexual reproduction.

• Incompatible mating types, the nuclei merge to form a diploid zygote, which in turn undergoes meiosis to form four sexually distinct haploid spores.

Growth And Development

Fungi exhibit distinctive growth patterns and developmental stages crucial to their ecological roles:

Hyphal growth:

• Most fungi are composed of large numbers of thread-like structures called hyphae, which are often branched and spread out to obtain nutrients.

• Thus, it aerates and stimulates the release of enzymes which decompose organic compounds that are in the soil.

Mycelium formation:

• Mycelium; as the hyphae grow and split they form a network referred to as mycelium.

• Mycelium is an individual vegetative structure of fungi and may be large, penetrating through the soil, substrates, or organism’s body. \

Classification Of Fungi

Fungi are classified into several major divisions (phyla) based on their reproductive structures and genetic characteristics:

Ascomycota (sac fungi):

• Members of this phylum contain sexual spores that develop in a slender container known as an ascus.

• Some of the examples that belong to this kingdom are yeasts, moulds such as Penicillium and truffles belonging to Tuber.

Basidiomycota (club fungi):

• Order Basidiomycetes include the formation of sexual spores called basidiospores, produced on flasks termed basidia.

• This group includes mushrooms such as Agaricus, rust-like fungi, and smut-like fungi.

Zygomycota (zygote fungi):

• Eubacteria can multiply both asexually through the production of spores as well as sexually through the production of round thick-walled zygospores from fused specialised hyphae.

• Some fungi are bread moulds (Rhizopus).

Other Groups

Deuteromycota (imperfect fungi):

• Also termed as deuteromycetes, they are fungi that have no understood sexual state of reproduction.

• They reproduce by spores and their examples are Aspergillus and Candida which are pathogens to human beings.

Fungal Diseases

Fungi cause a variety of diseases in plants, animals, and humans, impacting agriculture, ecosystems, and public health:

Plant Pathogens

Examples: The diseases which affect the body of plants are known as rusts and smut blights.

• Rusts: A group of diseases caused by fungi that infects a part of the plant such as the leaves and stems and has a reddish-brown powder-like formation.

• Smuts: Ascomycotina that, in the capacity of parasites, inhabit grains and grasses, giving the infected tissues a black, sooty appearance.

• Blights: Bacterial diseases leading to yellowing, withering and rotting of plant parts and particularly attacking commodities like potatoes and tomatoes.

Animal And Human Pathogens

Examples: Such as athlete’s foot, ringworm, candidiasis

• Athlete’s Foot: Commonly known as athlete’s foot, the disease is caused by dermatophyte fungi to infect the skin of feet resulting in itching, redness and peeling skin.

• Ringworm: Contrary to what the name suggests, ringworm is an infection of the skin or scalp by various fungi characterized by rashes forming circular patterns.

• Candidiasis: Some of the Candida genus yeasts, for example, Candida albicans are known to cause infections in different parts of the body including the mouth region (oral thrush), or the genital region (vaginal candidiasis).

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Beneficial Fungi

Fungi provide numerous benefits to humans and the environment through various applications:

Edible Mushrooms

They are nutritional sources of protein, fibre, vitamins especially B complexes and minerals for instance; selenium and potassium.

• Agaricus (Button Mushrooms): Commonly used for their bland taste and in many recipes requiring a bland-tasting ingredient.

• Shiitake: Popular for its tasty flavour and health benefits it contains substances that may help the body fight diseases and inflammation.

Medicinal Fungi

• Fungi are used as a source of bioactive compounds used in medicine for instance antibiotics- penicillin from Penicillium, immunosuppressants – cyclosporine from Tolypocladium inflatum.

• They cure infections and control immune disorders as well.

Bioremediation

• Some of the important functions regarding bioremediation that these fungi provide include the degradation of pollutants in earth, water, and gaseous media.

• Organic substances such as oils and fuel and hazardous wastes from industries possess adverse effects on the environment and they reduce these through degradation.