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Exploring Fungi: Pathogenesis and Mycology Fundamentals

Uncover the world of fungi and their pathogenic potential in this informative lecture by Dr. Ahmed M. Albarraq. Discover the distinguishing characteristics of fungi, their classification, reproduction, and identification processes. Delve into the study of medical mycology, fungal diseases (mycoses), and the morphological features of yeast and filamentous fungi. Learn how to differentiate between yeast and mold forms, understand spores, and explore the pathogenicity of fungi. Gain insights into the mechanisms by which fungi can cause diseases in humans. This foundational block in microbiology will equip you with essential knowledge for recognizing and understanding the impact of fungi in medical settings.

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Exploring Fungi: Pathogenesis and Mycology Fundamentals

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  1. Lecture Title: Fungi and their pathogenesis (Foundation Block, Microbiology) Lecturer name: Dr. Ahmed M. Albarraq Lecture Date: Oct.-2018

  2. Lecture Objectives.. • To describe the general characteristics of fungi and recognize a fungus from all other living organisms • To establish familiarity with the terminology needed by medical students • To know certain fundamental facts about classification reproduction and identification of fungi

  3. What is Mycology?.. Mycology: Study of fungi Kingdom myceteae (= Kingdom fungi) Medical mycology : Study of medically important fungi and the mycotic diseases. Mycoses: A disease caused by a fungus

  4. What is Mycology? There are five kingdoms

  5. What is a Fungus ? Characteristics (distinguishing features) • All Eukaryotic organisms (a true nucleus) • Heterotrophic (Saprobic, symbiotic, parasitic) • Do not have chlorophyll (Achlorophyllous) • The cell is surrounded by rigid cell wall made of chitin & complex carbohydates (Mannan, glucan) • Cell membrane : (sterol, ergosterol)

  6. What is a Fungus ? Characteristics (distinguishing features) Saprobic feed on dead tissues or organic waste (decomposers) Symbiotic mutually beneficial relationship between a fungus and another organism Parasitic feeding on living tissue of a host. (disease)

  7. MORPHOLGY • Yeasts : are unicellular organisms • Filamentous fungi (Hyphae, mycelium) Hyhpae are multicellular filamentous structures, constituted by tubular cells with cell walls. • Dimorphic • Yeast : Parasitic form, Tissue form, Cultured at 37° C • Filamentous : Saprophytic form, Cultured at 25 C Dimorphic: Have two forms depending on change in the environmental factors Mold form Yeast form

  8. MORPHOLGY • Yeast: Colony morphology (Culture) Have same appearance How do we differentiate between them? Budding yeast cell • In Clinical samples • Budding yeast cells • +/- Pseudohyphae Examples : Candida albicans, Saccharomyces cerevisiae

  9. MORPHOLGY • Filamentous fungi (Mould=Mold) A hypha (plural hyphae) is a long, branching filamentous cell. hyphae are the main mode of vegetative growth. Mycelium: The intertwined mass of hyphae that forms the fungal colony. Conidia/ Spore (singular = conidium): asexual spores borne externally on hyphae or on a conidiophore. Examples: Aspergillus, Penicillium, Rhizopus

  10. Filamentous fungi MORPHOLGY Penicillium, Colonial morphology Rhiaopus

  11. MORPHOLGY Filamentous fungiHyphal growth from spore Spore/ conidia mycelium

  12. Filamentous fungi MORPHOLGY

  13. MORPHOLGY • Filamentous fungi Conidia / spore (singular = conidium): asexual spores borne externally on hyphae or on a conidiophore. Conidia

  14. Fungal Hypha • Filamentous fungi Septa: Cross-walls (septa) that divide hyphae into segments. (septate hypha) If there are no cross-walls, the hyphae are considered to be non-septate. Non-Septate hypha Septate hypha

  15. MORPHOLGY • Filamentous fungi (mold) Moniliaceous mold hyaline or lightly pigmented conidia or hyphae, colorless Dematiaceous Mold Are pigmented. Because of the pigment, the colonies appear dark, brown, or black

  16. Reproduction in Fungi I) Asexual: Only mitotic cell division 1) Somatic Yeasts by budding Molds by hyphal fragmentation 2) Spore formation: a) Sporangiospores in sporangia b) Chlamydospores in or on hyphae c) Conidia (conidium) on hypha or on conidiophores II)Sexual: Fusion, mitosis, meiosis

  17. Reproduction in Fungi

  18. Spores? • These are the small airborne particles by which fungi reproduce. • They are produced by mitosis and readily disseminate in the air. SPORES

  19. PATHOGENICITY OF FUNGI • However, fungi can cause diseases to humans • Cause superficial infections, • some can cause allergic reactions • Few cause invasive infections • To cause the disease: • Thermotolerance • Ability to survive in tissue environment • Ability to withstand host defenses

  20. Thank You  (Foundation Block, Microbiology) Dr. Ahmed M. Albarraq Oct.-2018

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