Fungal Structure And Function Lecture Notes 2024-2025 PDF

Fungal structure and function MYCOLOGY SSCY 2613/SSCG 2633 Associate Prof Dr Madihah Md Salleh Dr Zarita Zakaria Department of Biosciences Faculty of Science Uiversiti Teknologi Malaysia Skudai, Johore Bahru Two types of scar are formed on yeast cells as a result of the division process: a si...

Fungal structure and function MYCOLOGY SSCY 2613/SSCG 2633 Associate Prof Dr Madihah Md Salleh Dr Zarita Zakaria Department of Biosciences Faculty of Science Uiversiti Teknologi Malaysia Skudai, Johore Bahru Two types of scar are formed on yeast cells as a result of the division process: a single 'birth scar' marking the point at which the cell was joined to the parent, and a variable number of 'bud scars' marking the points at which buds have been formed.  Spore Size - Puffball ❖Most molds reproduce by forming spores that disperse into the air in search of more food and moisture (similar to seed dispersal from plants) ❖Millions of spores being released into the atmosphere from a puffball ❖Most filamentous mold spores are microscopic and therefore, invisible to the naked eye 13  Reproduce by Spores ❖Spores are reproductive cells Sexual: plus (+) and minus (-) Asexual: budding or breaking hyphae ❖Formed Directly on hyphae Inside sporangia Fruiting bodies Above: Hyphae Middle: sporangia Far Left: fruiting body 1.Hyphae: Hyphae are the long, branched, and tubular projections of fungus that are involved in food absorption. 2.Mycelia: Mycelium or root-like structures of fungi that contain a mass of thread-like, branching hyphae.  Fungi Macro Structure ❖Composed of hyphae Thread-like structures ❖Each hypha is covered by a cell wall composed of chitin Chitin is a carbohydrate(replaces cellulose that we have) Same material that is found in hard shells of lobsters, insects, and spiders ❖Each hypha contains: Nuclei Cytoplasm Mitochondria Ribosomes ❖As hyphae grow longer, nuclei divide Cross-walls can form In others the cytoplasm ends up becoming multi-nucleated ❖The extensive branching networks of hyphae are called mycelium. The cell wall is a characteristic structure of fungi and is composed mainly of glucans, chitin and glycoproteins. As the components of the fungal cell wall are not present in humans, this structure is an excellent target for antifungal therapy. CHITIN: Fungal chitin is a component of the structural membranes and cell walls of mycelia, stalks, and spores. However, chitin is not found in all fungi (may be absent in a few sp.) Chitin, also found in the exoskeleton of insects, gives structural strength to the cell walls of fungi. The wall protects the cell from desiccation and predators. STEROL: Ergosterol, the major sterol found in fungal cell membranes, functions in the same capacity as cholesterol, the major sterol found in mammalian cell membranes maintain membrane fluidity, acting as signalling molecules for signal transduction pathways as important precursors for fat soluble vitamins and several hormones. might help reduce cholesterol levels by limiting the amount of cholesterol that is able to enter the body.  Hyphae Size Fruiting Body and Mycelium ❖ Hair 100 microns ❖ Hyphae belong to the genus Penicillium and they are about 2-4 microns across ❖ Fruiting Body Reproductive structure Grows from mycelium ❖ Mycelium Mass of branching hyphae below soil ❖ Example: Mushroom Hyphae of the water mold Saprolegnia Basis for Bacteria Fungi Comparison Definition Bacteria are single-cell microscopic Fungi, singular fungus, are eukaryotes that organisms that are characterized by are characterized by the presence of chitin the presence of incipient nucleus and in the cell wall. few membrane-less cell organelles Cell Type All bacteria are prokaryotes. All fungi are eukaryotes. No. of cells 0.5 to 5 µm. 2 to 10 µm. Cell wall ❖ Peptidoglycan ❖ Chitin ❖ Teichoic Acid ❖ Glucan ❖ Muramic Acid ❖ Mannan Morphology Bacteria are found to have three Fungi are found to have varying shapes, distinct shapes viz round (cocci), spiral but most of them are spotted in the form (Spirilla), and rod-shaped (bacillus). of a thread-like structure called hyphae. Nucleus The genetic material in bacteria is The genetic material in fungi is localized in localized in the nuclear region of the the nuclear region. cytoplasm. Cell organelles Bacteria have few membrane-less Fungi contain several membrane-bound organelles. organelles Ribosomes Bacteria like all prokaryotes contain Fungi, like all eukaryotes, contain 80S 70S ribosomes. 70S ribosomes consist ribosomes. The 80S ribosome is composed of 50S and 30S subunits. of two subunits 60S and 40S. Source of energy Bacteria derive their energy from Fungi obtain their energy from pre-existing inorganic matter or organic matter like organic matter. sugar, protein, or fat.  Ultra Structure of Fungi and Function Cell Description Function structure Cell wall Freely permeable layer Supports and strengthens cell surrounding cell membrane Cell Selectively permeable double Controls which substances can enter membrane layer of lipid and protein and leave the cell molecules Cytoplasm Fluid enclosed by the cell Location of many chemical reactions membrane, containing organelles and ribosomes Mitochondria Rod-shaped structures found in Location where aerobic respiration cytoplasm occurs and most of the cell's ATP is produced Ribosomes Small complexes found in Location where amino acids are cytoplasm connected together to produce proteins Plasmids Small circular DNA molecules Contains genes that help cell to function, eg genes for antibiotic resistance Nucleus Compartment in cell where Controls activities of cell DNA is stored as chromosomes  Function of Fungal Cell Wall ❖ This structure prevents the hyhae from bursting due to the processes of osmosis. ❖ The cell wall in mycelial fungi varies in thickness from about 50 nm (50 billionths of a metre) in the recently synthesized areas around the apex to 250 nanometres (250 billionths of a metre). ❖ PROTECTS the underlying protoplasm; ❖ Determines and MAINTAINS THE SHAPE of the fungal cell or hypha ❖ Acts as an INTERFACE between the fungus and its environment; ❖ Acts as a BINDING SITE for some enzymes; ❖ Possesses ANTIGENIC properties - which allow interactions with other organisms. The cell wall is a characteristic structure of fungi and is composed mainly of glucans, chitin and glycoproteins. As the components of the fungal cell wall are not present in humans, this structure is an excellent target for antifungal therapy. Glucan Biosynthesis and antifungal drugs ❖ Glucan is the major structural polysaccharide of the fungal cell wall, constituting approximately 50-60% of the wall by dry weight, ❖ Providing an appealing target for antifungal drugs. Inhibition of glucan biosynthesis destroys the structure of cell wall thus suppressing fungi growth and survival. ❖ The glucans of the fungal cell wall are polymers composed of repeating glucose residues that are assembled into chains through a variety of chemical linkages. ❖ In the process of glucan synthesis, glucan synthases are key enzymes which can act as the attractive targets for antifungal drugs.  Glycosylphos-phatidylinositol (GPI) Biosynthesis ❖ GPI functions as the bridge that anchors many functional proteins to the plasma membrane. ❖ These GPI-anchored proteins may function as glycosylhydrolases, glycosyltransferases, and peptidases which are responsible for cell wall synthesis and remodeling. ❖ Therefore inhibition of GPI biosynthesis provides an attractive potential target for the development of antifungal drugs. Chitin Biosynthesis ❖ Chitin is a β(1,4)-linked homopolymer of N-acetylglucosamine that present in all known fungal pathogens and not in humans. ❖ Therefore inhibition of chitin synthesis has been suggested as an attractive target for antifungal drugs. Mannoprotein Biosynthesis ❖ Mannoproteins are heavily glycosylated with chains rich in mannose. ❖ They are the major components of the fungal cell wall. ❖ Inhibition of mannoprotein biosynthesis can disrupt the mannoprotein outer layer of the cell wall and unmask the more immunogenic inner β-glucan layer. ❖ Thus mannoprotein biosynthesis also represents a target for the development of anti-fungal drugs.  Antifungal Drug – Mode of Action. ❖ Treatment of an antifungal disease is quite difficult than a bacterial infection. ❖ The reason is quite clear that most of the eukaryotic fungal cells have a lot in common with human cells, so antifungal drugs can also damage the host body cells. ❖ Also, some fungi have detoxification properties that can modify antifungal drugs and as a result, the effectiveness of these drugs will be reduced. ❖ There are several antifungal drugs that may be useful in treating fungal infections. ❖ These drugs are acted by extracting or preventing the synthesis of fungal membrane sterol without harming the mammalian cell, because of the fungal cell membranes have a unique sterol, called ergosterol, which replaces cholesterol found in mammalian cell membranes. ❖ Similarly, because fungal cell walls contain chitin, the enzyme chitin synthase is the target for antifungals such as polyoxin D and nikkomycin.  Fungi Cell Membrane Structure and Function ❖ Structure: bilayered Phospholipids Sterols (ergosterol, zymosterol) ❖ Functions Protects cytoplasm regulates the intake and secretion of solutes facilitates capsule and cell wall synthesis  Thank You for your attention