Introduction to Kingdom Fungi

Introduction to Kingdom Fungi

Fungus is derived from the Latin term for mushroom. Many types of fungi use the familiar mushroom which is a reproductive organ. On the other hand, many fungi species do not produce mushrooms at all.

A typical fungal cell has a functional nucleus and several membrane-bound vesicles, as it is a eukaryote. The Ascomycota or natural Fungi, are a unique bunch of living organisms that belong to the kingdom Fungi. 

The Kingdom Fungi belongs to the Eukarya realm and encompasses edible mushrooms, yeasts, black mould and Penicillium notatum, the manufacturer of the antibiotic penicillin. The kingdom fungi includes black dots on dry bread, yeast, white patches on mushrooms and mustard leaves. Fungi are unique from other kingdoms in their cell walls, such as bacteria, plants and a few protists. Fungi can only multiply and flourish in damp, humid environments. Although fungi are usually terrestrial organisms, they can be found in freshwater and marine water.

Structure

Fungi are eukaryotic organisms with non-vascular, spore-bearing, nucleated cell walls and bodies made up of long fine-branched strands. Except for unicellular yeasts, fungi are filamentous. The fungi structure comprises spores, food sources, sporangium and hyphae. In terms of a definite structure:

• Fungi lives in a damp, acidic environment and may grow in the absence of light or oxygen
• The nucleus in fungi is thick and includes chromatin strands
• Fungi can be unicellular, multicellular or dimorphic
• Mycelium is a network of hyphae that forms a mesh-like structure
• Fungi have a tangle of delicate, thread-like hyphae in their growing period, but the reproductive stage is usually more noticeable
• The cell walls of fungi are stiff and comprise chitin (which gives structural strength) and glucans, which are complex polysaccharides
• Ergosterol is a steroid molecule present in cell membranes of fungi that act as a substitute for cholesterol in animal cell membranes

Features

• Fungi do not have an embryonic stage
• A chemical called pheromone produced by fungus allows them to reproduce sexually
• In fungi, both sexual and genderless breeding is possible. Spores are used for reproduction
• As compared to bacteria, fungi develop slowly
• Fungi lack chloroplasts

Kingdom Fungi Classification

Kingdom Fungi are categorised either based on spore formation or nutrition. Based on nutrition, they are classified into –

1. Saprophytic Fungi live off and feed on dead organic waste. Saprophytic fungi is further grouped into Endophytic saprophytes that develop inside organic materials, while Ectophytic saprophytes grow on the surface. Some examples are Mucor, Rhizopus and Penicillium.
2. Parasitic fungi feed on their hosts, other living or dead creatures. They cause sickness in the hosts, which is harmful to them. Depending on where they live, there are two parasites: Ectoparasites that dwell on the host surface and Endoparasites that dwell inside the host body. They are symbiotic, meaning they feed and thrive on other living species.
3. Symbiotic fungi thrive on other living species. For instance, Lichens and mycorrhizae, both gain from each other.

Based on Spore formation, fungi are classified into:

1. Phycomycetes can be found on decomposing wood, wet surfaces, or damp settings. The mycelium is coenocytic and septate. Albugo, Mucor and Rhizopus are some typical examples
2. Ascomycetes are typically known as the sac-fungi. Typically found in a multicellular form and distinctive unicellular forms. Ascomycetes have mycelium that is forking and distinct. They might be freeloading, saprophytic, or decomposers. Aspergillus, Claviceps and Neurospora are some examples.
3. Fungi found in soil, tree stumps and logs are known as basidiomycetes. Their mycelium has developed into a spreading, distinct form. Basidiomycetes, which are commonly found as mushrooms, lack sex organs. Typical examples are Puccinia, Ustilago and Agaricus.
4. Deuteromycetes are also known as imperfect fungus. Deuteromycetes can only be identified when they are in the vegetative stage. Conidia, also known as asexual spores, are employed to reproduce and their mycelium is also branching and unique.  A few examples are Alternaria, Colletotrichum and Trichoderma.

Few generate multicellular organisms and hyphae (cells without septa), multinucleated (coenocytic). They produce gametes and diploid zoospores that use a single flagellum for swimming.

Development Process of Kingdom Fungi:

A fungus’ vegetative body is a thallus, unicellular or multicellular. Depending on the environment, dimorphic fungi can transform from unicellular to multicellular forms. Yeasts are the generic term for unicellular fungus. Unicellular fungi include Candida species (thrush agents, a common fungal infection) and Saccharomyces cerevisiae (baker’s yeast). Few generate multicellular organisms and hyphae (cells without septa), multinucleated (coenocytic). They produce gametes and diploid zoospores that use a single flagellum for swimming

The vast majority of fungi are multifunctional creatures. There are two distinct anatomical stages in which they might be found: vegetative and reproductive. The vegetative stage is marked by a knot of slender string structures known as hyphae (plural- hypha), whereas the reproductive stage is more apparent. A mycelium is a mass of hyphae. It can grow on a flat surface, in soil or decomposing debris, in liquids and even in live tissue. The mycelium of a fungus can be incredibly humongous, with certain species being “the fungus monstrous,” even though each hypha must be studied under a microscope.

Fungi thrive in damp, somewhat salty conditions and can grow in the presence or absence of light.

Reproduction of Kingdom Fungi:

In the Kingdom Fungi, they can reproduce asexually and sexually by disintegration, sprouting, or creating spores.

• The breaking of hyphae might result in the formation of new fungus colonies
• A bulge emerges on the side of the cell during branching and the bud eventually detaches after the core splits from multinucleated
• In fungi, sexual reproduction is frequently triggered by adverse environmental conditions
• In a community of fungus, sexual reproduction introduces evolutionary divergence. Sexual reproduction is common in fungus in response to adverse environmental conditions. Two forms of mating are created.  Homothallic or self-fertile when both mating kinds are present in the same mycelium. Heterothallic mycelia require two different yet compatible mycelia to reproduce sexually
• When it comes to sexual reproduction, mycelium can be homothallic or heterothallic
• The three stages of fungus sexual reproduction are plasmogamy, karyogamy and gametangia
• Plasmogamy- Fusion involves the union of cytoplasm as well as nuclei
• Karyogamy- Fusion of nuclei. In higher fungi, karyogamy is delayed and occurs just before meiosis. The Dikaryon stage (n+n) comes before karyogamy. It’s also called the resting stage
• Gametangia-  Gametes are produced by cells or organs. Gametes are fused in sexual reproduction
• Asexual spores are genetically similar to their parents and can be produced outside or inside a sporangium, a unique reproductive sac

Environmental Distribution:

Fungi can exist independently or as parasites of other eukaryotic organisms and can be found almost anywhere. Some species can withstand harsh environments, such as extreme temperatures: some can survive at temperatures as low as 5-6 degrees below zero, while others may survive at temperatures as high as 50 degrees. Mildews are microscopic fungi with a dusty white, gray, green, or black appearance and often appear as a blue or green covering on foods like bread, jam and fruits.

Conclusion:

Like humans, fungi are heterotrophs. They consume other plants or animals for energy and nutrients. The study of microscopic fungi falls under the scope of microbiology. Some microscopic fungi are useful in the food industry and make bread, wine and beer. They are essential for the recycling of inorganic resources and some saprophytic fungi function as decomposers. Others are important in the pharmaceutical industry and the industry of biotechnology.