What are fungi?
Fungi (singular is fungus) come comes from ancient Greek word ‘mukēs’ which means "fungus". Fungi refer to a diverse group of organisms that include yeasts, molds, and mushrooms. They are eukaryotic and mostly multicellular, but some are also unicellular. Fungi are important decomposers and play a crucial role in nutrient cycling in ecosystems. Some fungi are also used in the production of food and beverages such as bread, beer, and cheese. However, some fungi can also cause diseases in plants, animals, and humans.
Structure of the fungi
Fungi have a unique structure that distinguishes them from other organisms. Some of the main features of their structure include:
- Hyphae
- Mycelium
- Spores
- Rhizoids
- Septa
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Structure of the Fungi. Picture generated in BioRender.com |
1. Hyphae
Hyphae are thread-like structures that make up the body of a fungus. They are composed of chains of cells that are usually elongated and tubular in shape, with a diameter of around 2-10 micrometers. Hyphae grow from the tip, a process called apical growth, which enables the hyphae to penetrate and explore new substrates.
Cell wall: The cell wall of hyphae is made of chitin, a tough, flexible polysaccharide that provides rigidity and structural support. The chitin in the cell wall is often combined with other polymers such as glucans, mannans, and proteins, which can vary in composition and structure among different types of fungi.
Septate or non-septate: Hyphae can be either septate or non-septate. Septate hyphae have cross-walls called septa that divide the hyphae into individual cells. The septa have small pores called dolipores, which allow cytoplasm and organelles to move between cells. Non-septate hyphae, also called coenocytic hyphae, lack septa and contain many nuclei within a continuous cytoplasmic mass.
Mycelium: The mycelium, which is the main body of the fungus, is composed of a network of hyphae that spread through the substrate, absorbing nutrients through the cell wall and transporting them along the hyphae. This allows fungi to grow and spread efficiently, and to colonize a wide range of substrates.
Specialized hyphae: Some fungi have specialized types of hyphae. For example, rhizoids are specialized hyphae that anchor the fungus to a substrate and absorb nutrients. Haustoria are specialized hyphae that penetrate the cells of plant hosts, allowing the fungus to obtain nutrients directly from the host.
The structure and function of hyphae are key to the success of fungi in a wide range of ecosystems, allowing them to explore and colonize new substrates, absorb nutrients efficiently, and interact with other organisms in complex ways.
2. Mycelium
Mycelium is the vegetative part of a fungus, made up of a network of hyphae. It is the main body of the fungus and is responsible for absorbing nutrients from the environment. Mycelia can be found in a wide range of habitats, from soil and decaying plant matter to the surfaces of living plants and animals.
Enzymes: The mycelium grows by extending the tips of its hyphae, which penetrate the substrate and secrete enzymes to break down complex organic compounds into simpler molecules that can be absorbed by the fungus. The hyphae then transport these nutrients back to the mycelium, where they are distributed throughout the fungus.
Size: The mycelium can grow to enormous sizes, with some individual mycelia covering many hectares of land. These large mycelial networks can be important for nutrient cycling in ecosystems, breaking down complex organic matter and redistributing nutrients throughout the soil.
Symbiotic relationships: Mycelia can also play important roles in symbiotic relationships with other organisms. For example, mycorrhizal fungi form associations with the roots of plants, exchanging nutrients with the plant in a mutually beneficial relationship. The mycelium of the fungus helps the plant absorb nutrients from the soil, while the plant provides the fungus with carbohydrates produced through photosynthesis.
Fruiting bodies: The mycelium of some fungi can produce specialized structures called fruiting bodies, which are responsible for producing spores and dispersing them into the environment. These fruiting bodies can take on a variety of forms, such as mushrooms, puffballs, or brackets.
The mycelium is a key component of the structure and function of fungi, allowing them to absorb nutrients efficiently, interact with other organisms, and play important roles in nutrient cycling and ecosystem processes.
3. Spores
Spores are reproductive structures produced by fungi that play a critical role in the life cycle of these organisms. Fungal spores are usually single cells that are capable of developing into a new individual when conditions are favorable.
Reproduction: Spores can be produced in a variety of ways depending on the species of fungus. Some fungi produce spores directly on specialized hyphae called sporangiophores, while others produce them in fruiting bodies such as mushrooms or puffballs.
Shape and size: Fungal spores come in a variety of shapes and sizes, ranging from small and round to large and elongated. They can be produced asexually or sexually, depending on the species of fungus. Asexual spores are produced through mitosis, while sexual spores are produced through meiosis and fusion of gametes.
Dispersal: Fungal spores can be dispersed in a variety of ways, including wind, water, and animal vectors. Once they land on a suitable substrate, the spores can germinate and produce a new individual. The conditions necessary for spore germination can vary widely between different types of fungi, and can include factors such as temperature, humidity, and nutrient availability.
Role of spores in adaptation: Fungal spores play an important role in the ecology and evolution of fungi. They allow for the dispersal and colonization of new habitats, and can also be an important means of survival during unfavorable conditions. Fungi have evolved a wide range of spore types and dispersal mechanisms, allowing them to colonize a wide range of environments and adapt to changing conditions.
Use in industries: In addition to their ecological importance, fungal spores also have many practical uses. They are used in the production of foods such as cheese and soy sauce, and in the manufacture of antibiotics, enzymes, and other biotechnological products. Fungal spores are also important in medical research, as they can be used as a model organism to study genetics and development.
4. Rhizoids
Rhizoids are specialized structures that are found in some types of fungi, particularly those belonging to the Zygomycota and Chytridiomycota phyla. Rhizoids are filamentous structures that resemble roots, but they differ from true roots in several ways.
Structure: Rhizoids are not true roots, as they do not have vascular tissue and they do not perform the same functions as roots in higher plants. Instead, rhizoids serve as anchoring structures that help the fungus attach to the substrate and absorb nutrients. They are typically formed from specialized hyphae and can grow to varying lengths depending on the species of fungus.
Absorption of nutrients: Rhizoids are capable of penetrating the substrate and secreting enzymes to break down organic matter. This allows the fungus to absorb nutrients such as sugars, amino acids, and minerals from the substrate. Some fungi, such as the bread mold Rhizopus stolonifer, can produce large, visible rhizoids that can cover the surface of the substrate.Reproduction: In addition to their role in nutrient absorption, rhizoids can also play a role in the reproduction of fungi. In some species, such as the water mold Saprolegnia, rhizoids can produce specialized structures called gametangia, which contain the gametes that will fuse to form a new individual.
Adaptation: Rhizoids are an important adaptation that allows fungi to colonize a wide range of habitats and substrates. By anchoring themselves to the substrate and secreting enzymes to break down organic matter, fungi can obtain nutrients and survive in environments that are not accessible to other organisms. Rhizoids also play an important role in the ecology of fungi, allowing them to interact with other organisms and participate in nutrient cycling and decomposition processes.
5. Septa
Septa, also known as septum or crosswalls, are structures found in the hyphae of some types of fungi. They are typically thin, cross-shaped walls that divide the hyphae into individual cells. Septa are formed by the deposition of chitin and other structural components, and can be either perforated or imperforate.
Metabolic processes: Septa serve several important functions in the life cycle of fungi. First, they allow for the division of the hyphae into discrete cells, which can help to compartmentalize metabolic processes and prevent the spread of damage or infection. This is particularly important in multicellular fungi, where septa can help to separate different tissues and organs.
Movement of nutrients: Septa can also regulate the movement of nutrients and other substances between different parts of the fungus. Perforated septa contain small pores or channels that allow for the diffusion of small molecules, such as sugars and amino acids, between adjacent cells. This allows for the efficient transport of nutrients within the fungus.
Reproduction: In some types of fungi, such as the Ascomycetes, septa can also play a role in reproduction. During sexual reproduction, specialized hyphae called ascogenous hyphae can form within the mycelium. These hyphae are divided by septa into individual cells, each of which contains a single nucleus. The nuclei within these cells can undergo meiosis and mitosis to produce haploid ascospores, which are released into the environment.
Fruiting bodies: The presence or absence of septa can vary widely between different types of fungi. Some fungi, such as the Zygomycetes, lack septa entirely, while others, such as the Basidiomycetes, have highly specialized septa that can play a role in the formation of fruiting bodies.
Septa are an important adaptation that allows fungi to regulate metabolic processes, transport nutrients, and participate in reproduction. Their presence or absence can have a significant impact on the biology and ecology of different types of fungi.
Overall, the structure of fungi allows them to grow and spread efficiently, absorb nutrients from a wide range of substrates, and reproduce effectively.
Video lesson on structure of the fungi
Functions of fungi
Fungi play important roles in many different ecosystems and have a variety of functions. Some of the main functions of fungi include:
Decomposition: Fungi are important decomposers that break down dead organic matter and recycle nutrients back into the ecosystem. They play a crucial role in nutrient cycling in many ecosystems.
Symbiosis: Many fungi form symbiotic relationships with other organisms, such as plants or animals. For example, mycorrhizal fungi form associations with plant roots and help them absorb nutrients from the soil. Lichens are symbiotic associations between fungi and algae.
Food production: Fungi are used in the production of many different types of food and beverages. For example, yeasts are used to make bread, beer, and wine. Some cheeses are also made using fungi.
Biotechnology: Fungi are used in biotechnology for a variety of purposes, such as producing enzymes, antibiotics, and other useful compounds.
Disease: Some fungi can cause diseases in plants, animals, and humans. However, these pathogenic fungi are relatively few in number compared to the vast number of beneficial fungi.
Overall, fungi play important roles in many different aspects of life on Earth, from nutrient cycling and food production to biotechnology and disease.
Some Questions and Answers
1. What is the plural of fungus?
A. The plural of fungus is fungi.
2. List the main features of structure of fungi?
A. The main features of their structure include hyphae, mycelium, spores, septa, and rhizoids.
3. Define mycelium?
A. The mycelium, which is the main body of the fungus, is composed of a network of hyphae that spread through the substrate, absorbing nutrients through the cell wall and transporting them along the hyphae.
4. How fungi are used in biotechnology?
A. Biotechnology: Fungi are used in biotechnology for a variety of purposes, such as producing enzymes, antibiotics, and other useful compounds.
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