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Kingdom Fungi

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What are Fungi?

MVSAT 2024

Fungus is any of the approximately 144,000 known fungi species, including yeasts, rusts, smuts, mildews, moulds, and mushrooms. Many fungus-like species, such as slime moulds and oomycetes, do not belong to the kingdom fungi yet are commonly referred to as fungi. The creatures in the kingdom fungi have a cell wall and are widely distributed. Among living beings, they are categorised as heterotrophs. 

Fungi are heterotrophic, meaning they get their energy and carbon from complex organic substances rather than sunlight. Animals and fungi are more closely linked than plants. Fungi can reproduce asexually, sexually, or both ways. The majority of fungi create spores, which are haploid cells capable of mitosis and becoming multicellular, haploid people.

The article deals with the explanation of what is fungi, fungi examples. Although there are different types of fungi, the article describes the generalised characteristics of the kingdom fungi.

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Fungi Cell Structure 

Fungi can be unicellular or multicellular. They are heterotrophic decomposers with strong cell walls that devour decomposing stuff and form thread entanglement. The hard cell walls of fungi include complex polysaccharides termed chitin and glucans, which provide mechanical rigidity. Ergosterol is a steroid component present in the cellular membrane that substitutes cholesterol in biological membranes. Fungi can be unicellular, multicellular, or dimorphic, which means that the fungi can be unicellular or multicellular based on the environment. The vegetative stage of fungi is characterised by a tangle of slender, thread-like hyphae, but the reproductive stage is generally more visible.

Fungi are eukaryotic organisms with complicated cellular structures. Fungal cells, like other eukaryotes, have a membrane-bound nucleus with DNA wrapped around the histone proteins. A few fungi contain structures that are similar to bacterial plasmids. Mitochondria and a complex system of internal membranes, including the endoplasmic reticulum and Golgi apparatus, are also found in fungal cells. Chloroplasts and chlorophyll are not found in fungus cells. Many fungi have vibrant hues, ranging from red to green to black, that are caused by different cellular pigments. 

Chitin and glucans are complex polysaccharides found in the stiff regions of cell walls. The structural strength of fungal cell walls is provided by chitin, which is also present in the exoskeleton of insects. The cell's wall protects it from dehydration and predators. Fungi possess phospholipid bilayers comparable to those of other eukaryotes, except that ergosterol, a steroid compound that substitutes cholesterol in animal cell membranes, stabilises the structure. The majority of kingdom  Fungi members do not move.

Growth in Kingdom Fungi

A fungal cell's vegetative body is known as the thallus, which can be unicellular or multicellular. Based on the environment, the dimorphic fungus can transition from single-celled to multicellular states. Yeasts are the common name for unicellular fungus. Unicellular fungi examples include Saccharomyces cerevisiae, also known as baker's yeast and Candida species, the agents of thrush, a common fungal illness. The vast majority of fungi are multicellular entities. There are two main morphological phases in which they might be found: vegetative and reproductive. 

The vegetative stage is characterised by a tangle of slender thread-like structures known as hyphae. A mycelium is a mass of hyphae. It may grow on a surface, in soil or decomposing matter, liquids, and even live tissue. The mycelium of a fungus can be quite enormous, even if individual hyphae must be examined under a microscope. Endwalls termed septa partition most fungal hyphae into distinct cells. In most fungi phyla, microscopic openings in the septa allow nutrients and small molecules to pass quickly from cell to cell along the hypha. Perforated septa are how they're described. Fungi thrive in damp, somewhat acidic settings and may grow in the presence or absence of light.

Nutrition in Kingdom Fungi

Since we have learnt about fungi, the fungi cell structure and fungi examples let us look into the nutrition in kingdom fungi. Fungi, like mammals, are heterotrophs, meaning they get their carbon from complex organic substances instead of from the environment. Furthermore, the fungus does not absorb atmospheric nitrogen. In contrast to most mammals, which absorb food and then digest it inside specialised organs, the fungus does the opposite: digestion comes before ingestion. Exoenzymes will be first transferred out of the mycelium and into the atmosphere, where it digests food. The organic particles created by external digestion are then ingested by the mycelium's vast surface area. Instead of the starch found in plants, glycogen is the polysaccharide of preservation.

Fungi are usually saprophytes or microorganisms that get their nourishment from decomposing organic materials. They get their nourishment from rotting or dead organic waste, primarily plant materials. Exoenzymes from fungi can convert intractable polysaccharides like cellulose and lignin from decaying wood into easily absorbed glucose molecules. As a result, carbon, nitrogen, and other elements are released into the atmosphere. Fungi have a significant ecological function and are being studied as possible bioconversion techniques due to their diverse metabolic processes.

Reproduction in Fungi

Fungi may reproduce in both sexual and asexual ways. Imperfect fungi reproduce exclusively asexually, whereas perfect fungi reproduce both sexually and asexually (by mitosis). Fungi release spores that disseminate from the parent organism by drifting on the wind or catching a ride on an animal in both sexual and asexual reproduction. Plant seeds are larger and heavier than fungal spores. The massive puffball mushroom erupts, releasing trillions of spores. The large quantity of spores expelled improves the chances of their landing in a growth-friendly environment.

Types of Fungi

Let us look into the classification to understand the different types of fungi. Kingdom fungus may be divided into three groups based on its nutritional needs.

  • Saprophytic Fungus - The saprophytic fungus gets its sustenance from dead organic matter. Rhizopus, Penicillium, and Aspergillus are some of the fungi examples.

  • Parasitic Fungus - The parasitic fungus gets its sustenance by living on other living things and absorbing resources from them. Taphrina and Puccinia are two parasitic fungi examples.

  • Symbiotic - Symbiotic fungi are those that exist in an interdependent relationship with other species in which both parties benefit. Lichens and mycorrhizae are two examples. Lichens are the result of a symbiotic relationship between algae and fungus. Algae and fungus benefit from each other in this situation since fungi offer shelter for algae and algae give shelter for fungi.

There are different types of fungi based on their spores, which are mentioned below.

  • Zygomycetes - These are made up of two distinct cells that have fused together. Asexual spores are called sporangiospores, whereas sexual spores are called zygospores. The septa are missing from the hyphae.

  • Ascomycetes - Also known as sac fungi, are a kind of ascomycetes. Ascospores refer to sexual spores. Conidiospores are used for asexual reproduction. Saccharomyces cerevisiae is a good example of this type.

  • Basidiomycetes - The most prevalent basidiomycetes are mushrooms, which mainly survive as parasites. Basidiospores are responsible for sexual reproduction. Conidia, budding, and fragmentation are all examples of asexual reproduction. Agaricus is a good example.

In conclusion of the article, we have seen the fungi information on form and function of fungi, we have seen the fungi examples. The growth and reproduction of fungi are also being discussed. 

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FAQs on Kingdom Fungi

1. What is fungi and the importance of fungi?

In human life, fungi play a crucial role. They are significant in medicine because they produce antibiotics, agriculture because they maintain soil fertility, and many industries because they are consumed as food.   They play a key role in the ecosystem's nutrient cycle. They're also insecticides. Most animal pathogens are fungi. As a result, they aid in insect population management.  They target certain insects in particular. The insecticide Beauveria bassiana is used to stop the spread of the emerald ash borer.

2. Explain sexual reproduction in fungi

In a community of fungus, sexual reproduction introduces genetic variety. Sexual reproduction is common in fungus in response to harsh environmental circumstances. There are two forms of mating that are created. It's called homothallic when both mating kinds are present in the same mycelium. To reproduce sexually, heterothallic mycelia require two distinct yet compatible mycelia. 

Although there are many different types of fungal sexual reproduction, all of them comprise the three steps below. First, two haploid cells fuse during plasmogamy (cytoplasm union), resulting in a dikaryotic stage in which two haploid nuclei coexist in a single cell. The haploid nuclei unite to produce a diploid zygote nucleus during karyogamy. Finally, meiosis occurs in the gametangia which produce gametes of various mating types. Spores are distributed throughout the environment at this point.

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