FUNGI |Definition, Cell Structure and Types:

What is Fungi?

The fungi(sing: fungus) are eukaryotic heterotrophic organisms consisting of filamentous separate or aseptate somatic structures called hyphae that generally  forms a woolly mass  called mycelium.

Its cell wall is made up of chitin or cellulose, or sometimes both.

They can reproduce both by sexual and asexual reproductions.

Occurrence:

They are present on almost everywhere on the earth from northern to southern hemispheres. Till today, their 80,000 species has been discovered and described.

However, they are more abundant in moist and shady areas. As already mention ed enjoy your unable to produce their own food that's why they tend to live as a saprobes on the abiotic organic matter ,causing it to decay; or those parasites that infect that can cause serious diseases in plants and human beings.

The fungi digest their organic food outside the body by secretion of extracellular   enzymes and making the organic matter soluble so that it may be absorbed by the mycelium.

Plant body:

Though, some fungi are unicellular but their is majority have multicellular plant body composed of thread like structure hyphae.

The hyphae is present in the form of loosely woven or interconnected mass, the mycelium. 

Since fungi lack vascular tissues, stem, roots and leaves, therefore, a division of labour is usually absent, and the plant body is in the form of thallus.

Hyphae:

A hypha is made up of a thin and transparent tabular wall lined with a layer of protoplasm. In primitive fungi, the hyphae are aseptate and coenocytic containing many nuclei inserted in cytoplasm.

In advanced fungi, the hyphae are septate,  divided into compartments by cross walls called septa.

In basidiomycetes, the septum is perforated which allows collection between the all portions of mycilium. It also allows the migration of nucleus from one cell to another.

Mycelium:

Mycelium is the vegetative part of a fungus, consisting of a network of thread-like structures called hyphae. Hyphae are thin, elongated cells that grow and branch out to form a complex, interconnected network. When hyphae grow and form a visible mass, it is referred to as mycelium.

If the mycelium penetrates the host's is tissue that it is referred as intercellular mycelium.It remains confined to the pustules in rusts and smuts,and  this type of fungus is called localized fungus.

In some cases, the mycelium can infect the entire plant body and it is called systemic fungus.

Cell structure:

The fungal cells are typically eukaryotic, non motile and lack chloroplasts in them. Its protoplst is formed by cell wall which is made up of chitin and other complex carbohydrates, but very little or no cellulose.

Plasmalema is another membrane hidden inside the cell wall that that acts as a unit membrane composed of protein layers separated by lipid layer.

In some fungi, a large vacuole bound by tonoplast is present whereas in other fungi many small vacuoles may be found.

The protoplasm of fungal cell is enriched with endoplasmic reticulum which may be coated with the ribosomes or without.

mitochondria are also plenty in it's cell specially in some apical vision of hyphae.

Golgi Apparatus is quite rare in fungal cells however where they are present there are 

4-5 cisternae.

With the few exceptions in the tips of hyphae, a number of microtubules may be found in it. Microtubules are involved in the transport of organelles and vesicles within the fungal cell. They form tracks along which these organelles and vesicles can move, allowing for efficient intracellular transport.

Microtubules also help in integrity of cell wall and support the cell to maintain their shape.

Ribosomes live either freely or maybe connected with rough endoplasmic reticulum (RER).

Their are main function is always the synthesis of protein.

Mostly fungi possess a highly organised nucleus, double membrane nuclear envelope, a nucleolus, and strand of thread like chromatin material.

During cell division, their does not disintegrate in prophase.Intead, the nuclear envelope constricts in dump bell shape and divides into two nuclei.

The centrioles play important role in spindle formation

The nucleolus mainly consists of RNA and behaves differently in different species of fungi during karyokinesis

.

Types of Fungi:

Fungi are a diverse group of organisms that can be found in almost every environment on earth. There are several types of fungi, which can be broadly classified based on their morphology, mode of reproduction, and ecological role.

There are currently around 8 recognized phyla of fungi, although the exact number may vary depending on the classification system used. These phyla are:

1) Zygomycota:

Zygomycota is a phylum of fungi that are fast-growing and commonly found in soil, decaying plant and animal matter, and in association with insects. These fungi reproduce sexually by forming large, sturdy structures called zygosporangia, which contain spores that can remain dormant for long periods of time. Zygomycota includes many economically important fungi, such as those used to produce tempeh and other fermented foods, as well as some plant and animal pathogens. Some zygomycetes are also used in bioremediation, such as for cleaning up contaminated soil and water.

2) Ascomycota:

Ascomycota, also known as sac fungi, is a phylum of fungi that includes over 64,000 species. They are characterized by the production of specialized sexual spores called ascospores, which are produced in structures called asci. Ascomycota can be found in a wide range of habitats, from soil and plant surfaces to freshwater and marine environments. Some species are important decomposers, breaking down dead plant material, while others are plant pathogens or symbionts. Ascomycota also includes many species of edible and medicinal fungi, such as morels, truffles, and penicillin-producing molds.

3) Basidiomycota:

Basidiomycota is a phylum of fungi that includes the mushrooms, toadstools, and bracket fungi. These fungi are characterized by their reproductive structures, called basidia, which produce sexual spores called basidiospores. Basidiomycota can be saprophytic, decomposing dead organic material, or symbiotic, forming mutualistic associations with plant roots or other organisms. Some species of Basidiomycota are also known to be important plant pathogens.

Basidiomycota are ecologically important decomposers and play a critical role in nutrient cycling in many ecosystems. They are also of economic importance as a source of food, medicine, and industrial products.

4) Deuteromycota: 

Deuteromycota, also known as fungi imperfecti, is a taxonomic group of fungi that do not have a known sexual reproductive stage.

These fungi are often characterized by their asexual spores, which are produced through various means such as budding or fragmentation.

Deuteromycota include a wide range of fungi, including some that are important plant pathogens, others that are used in the production of food and pharmaceuticals, and some that are common indoor allergens.

6) Chytridiomycota

Chytridiomycota is a phylum of fungi that are primarily aquatic, although they can also be found in soil and other moist environments. These fungi are unique among fungi because they have a flagellated spore stage, called a zoospore, which allows them to swim through water. Chytrids can be saprophytic, decomposing dead plant and animal material, or parasitic, infecting plants, animals, and even other fungi. Some species of chytrids are important decomposers in aquatic ecosystems, while others can cause serious diseases in amphibians and have been implicated in global declines in amphibian populations.

7) Neocallimastigomycota:

Neocallimastigomycota is a phylum of anaerobic fungi that inhabit the digestive tracts of herbivores, including cows, sheep, and deer.

These fungi are capable of breaking down the complex polysaccharides found in plant cell walls, such as cellulose and hemicellulose, which are otherwise indigestible to the host animal.

The fungus gains access to the nutrients released from the plant material, while the animal is able to derive energy and nutrients from the breakdown products of the fungal activity.

Neocallimastigomycota have a unique morphology, with small, spherical cells called zoosporangia that release motile spores called zoospores. They are an important component of the microbial communities in the digestive tracts of herbivores and are crucial for the breakdown of plant material in the gut.

8) Glomeromycota:

Glomeromycota is a phylum of fungi that includes the arbuscular mycorrhizal fungi (AMF). These fungi form mutualistic associations with the roots of plants, in which the fungus provides the plant with essential nutrients such as phosphorus and nitrogen, while the plant provides the fungus with carbohydrates. AMF are found in the roots of the majority of land plants, including crops and trees, and are important for plant growth and survival. Glomeromycota is characterized by its asexual mode of reproduction, in which multinucleate spores are produced.

The taxonomy and phylogeny of Glomeromycota are still not fully resolved, but recent advances in molecular biology have helped to shed light on the evolutionary relationships between the different members of this phylum.

Conclusion:

In short, fungi are a fascinating and important group of organisms that play diverse roles in the natural world. While they have many beneficial uses, it is important to be aware of the potential harm that some species of fungi can cause and to take appropriate precautions to avoid exposure to harmful fungi.

Frequently Asked Questions-FAQs

1. What is the most common fungi?

The members of Phylum Basidiomycotamycota is among the most abundant types of fungi.This group includes  nearly 16,000 species including mushrooms, puffballs, toadstools and bracket fungi.

2. What is hyphae?

Hyphae are thread-like structures that make up the body of a fungus. They are long, narrow, and can be either septate (divided by walls) or non-septate (without walls).Hyphae can vary in size, from just a few micrometers in diameter to several millimeters, depending on the species of fungus.

3. What is mycelium?

Mycelium is the vegetative part of a fungus, consisting of a network of branching, thread-like structures called hyphae.Mycelium is responsible for the absorption of nutrients from the environment, as it secretes enzymes that break down organic matter into simpler compounds that can be taken up by the hyphae.

4. Which type of fungi can move?

Chytridiomycota are unique among fungi because they have a flagellated spore stage, called a zoospore, which allows them to swim through water. Chytrids can be saprophytic, decomposing dead plant and animal material, or parasitic, infecting plants, animals, and even other fungi.

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