Concordia University Of Edmonton BES 108D Fungi Lecture 11 PDF

1 Lecture 11- Feb 3 2025 rd BES 108D Organisms in their environment By Dr. Benazir Alam [email protected] Copyright © 2025 Pearson Canada, Inc. 29 - 1  2 Chapter 31 Fungi Copyright ©...

1 Lecture 11- Feb 3 2025 rd BES 108D Organisms in their environment By Dr. Benazir Alam [email protected] Copyright © 2025 Pearson Canada, Inc. 29 - 1  2 Chapter 31 Fungi Copyright © 2025 Pearson Canada, Inc. 29 - 2 Fungi Fungi are heterotrophs and absorb nutrients from outside of their bodies Fungi that are decomposers use hydrolytic enzymes to break down a large variety of complex molecules into smaller organic compounds from nonliving organic material, such as fallen logs, animal corpses, and the wastes of organisms into glucose, amino acids, nucleic acids and fatty acids. Fungi are efficient decomposers of organic material including cellulose and lignin Some parasitic fungi use enzymes to penetrate the walls of living cells, enabling the fungi to absorb nutrients from the cells. Collectively, the different enzymes found in various fungal species can digest compounds from a wide range of sources, living or dead, including the most abundant biomolecules on the planet—cellulose and lignin. Mutualistic fungi can form symbiotic associations with plant roots. These relationships enhance nutrient absorption for plants, particularly phosphorus, while providing the fungi with carbohydrates produced through photosynthesis. Copyright © 2025 Pearson Canada, Inc. 29 - 3 The Role of Fungi in the Ecosystem Copyright © 2025 Pearson Canada, Inc. 29 - 4 Body Structure (1 of 2) Most common body structures are multicellular filaments and single cells (yeasts) Some species grow as either filaments or yeasts; others grow as both Copyright © 2025 Pearson Canada, Inc. 29 - 5  Body Structure (2 of 2) The morphology of multicellular fungi enhances their ability to absorb nutrients Gills Fungi consist of mycelia, networks of branched hyphae adapted for absorption A mycelium’s structure maximizes its surface area-to-volume ratio Fungal cell walls contain chitin, a strong & flexible nitrogen-containing Gills polysaccharide that enhances absorption Copyright © 2025 Pearson Canada, Inc. 29 - 6  7 Mycelium ❑ Fungal hyphae form an interwoven mass called a mycelium ❑ The structure of a mycelium maximizes its surface-to- volume ratio, making absorption of nutrients very efficient. Just 1 cm3 of rich soil may contain as much as 1 km of hyphae with a total surface area of 300 cm2 in contact with the soil. Gills ❑ A fungal mycelium grows rapidly, as proteins and other materials synthesized by the fungus move through cytoplasmic streaming to the tips of the extending hyphae. ❑ The fungus concentrates its energy and resources on adding hyphal length and thus overall absorptive surface area, rather than on increasing hyphal girth. ❑ Multicellular fungi can move into new territory, swiftly by extending the tips of their hyphae. Copyright © 2025 Pearson Canada, Inc. 29 - 7  Think….. What is the advantage of mycelia? Copyright © 2025 Pearson Canada, Inc. 29 - 8 Fungal Reproduction and Nutrition Copyright © 2025 Pearson Canada, Inc. 29 - 9 Specialized Hyphae in Fungi and plants Mycorrhizae are mutually beneficial relationships between fungi and plant roots Foresters even commonly inoculate pine seedlings with mycorrhizal fungi before planting to promote growth. Nutrients are transferred between different trees via the mycorrhizal network Most vascular plants have mycorrhizae Mycorrhizal fungi deliver phosphate ions and minerals to plants Mycorrhizal fungi colonize soils by the dispersal of spores that forms a new mycelia after germinating Copyright © 2025 Pearson Canada, Inc. 29 - 10  Specialized Hyphae in Mycorrhizal Fungi (2 of 2) Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into extracellular spaces of the root cortex Endomycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of root cell membrane This close interaction allows for more direct and efficient transfer of nutrients like phosphorus, nitrogen, and micronutrients to the plant. Hence, about of all plant species ~85% have mutualistic partnerships with Also known as Haustoria arbuscular mycorrhizae Copyright © 2025 Pearson Canada, Inc. 29 - 11  Fungi produce spores through sexual or asexual life cycles Fungi propagate themselves by producing vast numbers of spores, from different types of life cycles (sexual or asexual). In asexual reproduction, fungi produce asexual spores through mitosis, which are genetically identical to the parent organism. Asexual reproduction allows fungi to quickly colonize new areas, as the spores can be dispersed widely. Sexual reproduction involves the fusion of two genetically different fungal cells (usually from different mating types), followed by meiosis, which leads to the production of sexual spores. This type of reproduction ensures genetic diversity. Copyright © 2025 Pearson Canada, Inc. 29 - 12  Sexual Reproduction Sexual reproduction requires fusion of hyphae (n) from different mating types Fungi use sexual signalling molecules called pheromones to communicate their mating type The pheromones from each partner bind to receptors on the other, and the hyphae extend toward the source of the pheromones. When the hyphae meet, they fuse. Plasmogamy is the union of cytoplasm from two parent mycelia In most fungi, haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called dikaryotic Hours, days, or even centuries may pass before occurrence of karyogamy, nuclear fusion can occur During karyogamy, haploid nuclei fuse, producing diploid cells Diploid phase is short-lived and undergoes meiosis, producing haploid spores The paired processes of karyogamy and meiosis produce genetic variation Copyright © 2025 Pearson Canada, Inc. 29 - 13  14 Plasmogamy Karyogamy Fusion of hyphal Fusion of cytoplasm haploid nuclei Copyright © 2025 Pearson Canada, Inc. 29 - 14 Asexual Reproduction In addition to sexual reproduction, many fungi can reproduce asexually by growing as filamentous fungi that produce haploid spores by mitosis Penicillium, a mould commonly Unicellular yeasts Saccharomyces encountered as a decomposer of cerevisiae reproduce asexually by food, produce haploid spores by simple cell division and pinching of mitosis and form visible mycelia. “bud cells” from a parent cell Copyright © 2025 Pearson Canada, Inc. 29 - 15  16 Alternation of generation in fungal life cycle Copyright © 2025 Pearson Canada, Inc. 29 - 16  The Move to Land Fungi were most likely derived from protists. Fungi were among the earliest colonizers of land and probably formed mutualistic relationships with early land plants Copyright © 2025 Pearson Canada, Inc. 29 - 17 Basidiomycetes Basidomycetes include mushrooms, puffballs, and shelf fungi. Basidiomycetes also called club fungi because of their distinctive reproductive structures called basidia, which resemble club shapes. This phylum also includes mutualists that form mycorrhizae and two groups of destructive plant parasites: rusts and smuts. Many basidiomycetes are decomposers of wood because of their ability to break down the complex polymer lignin, an abundant component of wood. Life cycle of basidiomycete usually includes long-lived dikaryotic mycelium Copyright © 2025 Pearson Canada, Inc. 29 - 18  Basidiomycetes In response to environmental stimuli, the mycelium reproduces Basidiocarp sexually by producing elaborate fruiting bodies called basidiocarps Gills Mushrooms are examples of lined basidiocarps with basidia Numerous basidia in basidiocarp are sources of sexual spores called basidiospores Basidiomycetes can produce mushrooms quickly Copyright © 2025 Pearson Canada, Inc. 29 - 19 Fungus-Plant Mutualisms Mycorrhizae are enormously important in natural ecosystems and agriculture Plants harbour harmless symbiotic endophytes (they are not the same as Arbuscular mycorrhizal fungi/Endomycorrhizae), fungi that live inside leaves or other plant parts Endophytes can benefits their host plants via helping in enhanced growth, increased resistance to pathogens, and improved stress tolerance. In grass and other non woody plants, endophytes make toxins that deter herbivores or by increasing host plant tolerance of heat, drought, or heavy metals Copyright © 2025 Pearson Canada, Inc. 29 - 20 Fungus-Animal Symbiosis Leaf cutter ants scour tropical forests in search of leaves, which they cannot digest on their own but carry back to their nests and feed to the Fungus-gardening insects fungi As the fungi grow, their hyphae develop specialized swollen tips that are rich in proteins and carbohydrates. The ants feed primarily on these nutrient-rich tips. Not only do the fungi break down plant leaves into substances the insects can digest, but they also detoxify plant defensive compounds that would otherwise kill or harm the ants. Copyright © 2025 Pearson Canada, Inc. 29 - 21 Fungi as Pathogens (1 of 4) About 30% of known fungal species are parasites or pathogens, mostly on or in plants Each year, 10% to 50% of the world’s fruit harvest is lost due to fungi Some fungi that attack food crops are toxic to humans Copyright © 2025 Pearson Canada, Inc. 29 - 22 Fungi as Pathogens (2 of 4) The general term for a fungal infection in animals is mycosis Ringworm and athlete’s foot are examples of human mycoses Copyright © 2025 Pearson Canada, Inc. 29 - 23  Practical Uses of Fungi (3 of 4) Humans eat many fungi (mushrooms and baker’s yeast) and use others to make cheeses, alcoholic beverages, and bread Some fungi produce antibiotics for treatment of bacterial infections – For example, the ascomycete Penicillium The mould Penicillium produces an antibiotic (penicillin) that inhibits the growth of Staphylococcus bacteria, resulting in the clear area between the mould and the bacteria Copyright © 2025 Pearson Canada, Inc. 29 - 24 Practical Uses of Fungi (4 of 4) Genetic research on fungi is leading to applications in biotechnology. For example: – Saccharomyces is being used to study homologs of genes involved in Parkinson’s and Huntington’s diseases – Insulin-like growth factor can be produced in Saccharomyces cerevisiae – Gliocladum roseum, a fungus that produces hydrocarbons similar to diesel fuel, could be used to produce biofuels Copyright © 2025 Pearson Canada, Inc. 29 - 25