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General Properties of Fungi Sevtap Arikan, MD

General Properties of Fungi Sevtap Arikan, MD. FUNGUS. Widely distributed in nature (air, water, soil, decaying organic debris) ~400,000 types Eukaryotic, highly developed cellular structure Facultatively anaerobic/strict aerobic Chemotropic, nutrition: by absorption Nonphotosynthetic.

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General Properties of Fungi Sevtap Arikan, MD

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  1. General Properties of FungiSevtap Arikan, MD

  2. FUNGUS • Widely distributed in nature (air, water, soil, decaying organic debris) • ~400,000 types • Eukaryotic, highly developed cellular structure • Facultatively anaerobic/strict aerobic • Chemotropic, nutrition: by absorption • Nonphotosynthetic

  3. Terminology • Mykos: Fungus • Mycoses: A disease caused by a fungus • Mycology: Study of fungi

  4. Major Developments in Mycology • Increase in number of immunocompromised patients • Newly developed antifungal drugs • Antifungal susceptibility testing • Resistance to antifungal drugs

  5. Fungi- Morphological Classification • Yeast • Mould • Dimorphic

  6. YEAST • Unicellular • Micr.: Oval to round (Dia: 3-15 µm) Reproduce by budding Bud=Blastospore Pseudohyphae • Macr.: Pasty colonies (resemble bacteria)

  7. MOULD • Multicellular Micr.: Hypha(e) (dia: 2-10 µm) Spores Macr.: Surfacetexture: Cottony/ wooly/ velvety/ granular... Pigmentation: observed from the reverse

  8. Mould-Definitions • Hypha • Mycelium: a. Vegetative b. Aerial

  9. Classification of Hyphae BASED ON: A. Existence of septa Septate Nonseptate B. Shape and Morphology Racquet Spiral Nodular Root-like (rhizoid) Pectinate Chandler

  10. DIMORPHIC • Capable of growing in mould or yeast form under different environmental conditions (temperature, CO2, nutrients) • Thermal dimorphism (a group of pathogenic fungi)

  11. Subcellular Structure of Fungi • Capsule (present only in some fungi) • Cell wall • Cell membrane • Cytoplasm Nucleus, nuclear membrane, nucleolus, ER, mitochondria, vacuoles

  12. CAPSULE Structure: Polysaccharide Functions: -Antiphagocytic -Virulence factor • Exist only in some fungi Cryptococcus neoformans (encapsulated yeast)

  13. CELL WALL • Antigenic in nature Structure: Multilayered a. polysaccharides (~90%): hexose and hexosamine polymers b. proteins and glycoproteins (~10%) Functions: Provides shape, rigidity, strength and protection from osmotic shock

  14. Major polysaccharides of fungal cell wall POLYMERMONOMER Chitin N-acetyl glucosamine Chitosan D-Glucosamine Cellulose D-Glucose -Glucan D-Glucose -Glucan D-Glucose Mannan D-Mannose • The type and amount of the polysaccharide vary from one fungal species to other.

  15. CELLULAR MEMBRANE Structure: Bilayered Phospholipids Sterols (ergosterol, zymosterol) Functions: a. Protects cytoplasm b. regulates the intake and secretion of solutes c. facilitates capsule and cell wall synthesis

  16. FUNGAL SPORES • Spores function in reproduction of fungi. 1. Sexual reproduction --Sexual spores 2. Asexual reproduction--Asexual spores 3. Parasexual reproduction--Genetic exchange

  17. SEXUAL SPORES 1. Zygospore 2. Ascospore 3. Basidiospore 4. Oospore

  18. ASEXUAL SPORES 1. Arthrospore 2. Blastospore 3. Chlamydospore 4. Macroconidium 5. Microconidium 6. Sporangiospore

  19. Fungi-Taxonomic classification • Depends primarily on the type of sexual spore Phylum -mycota Class -mycetes Order -ales Family -ceae Genus Species

  20. Fungi-Taxonomic classification SEXUAL SPORECLASS Zygospore----------Zygomycetes Basidiospore--------Basidiomycetes Ascospore----------Ascomycetes None/Unknown---- Deuteromycetes (“Fungi Imperfecti”)

  21. MYCOSES • Superficial (Hair, skin, nail, cornea) • Subcutaneous • True systemic (endemic) • Opportunistic

  22. LABORATORY DIAGNOSIS OF MYCOSES • Direct microscopic examination Gram, potassium hydroxide (KOH), calcofluor white, India ink • Culture Sabouraud dextrose agar Mycobiotic agar • Serology

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