General Properties of Fungi Sevtap Arikan, MD

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General Properties of FungiSevtap Arikan,
MD
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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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Terminology

• Mykos Fungus
• Mycoses A disease caused by
• a fungus
• Mycology Study of fungi

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Major Developments in Mycology

• Increase in number of immunocompromised patients
• Newly developed antifungal drugs
• Antifungal susceptibility testing
• Resistance to antifungal drugs

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Fungi- Morphological Classification

• Yeast
• Mould
• Dimorphic

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YEAST

• Unicellular
• Micr. Oval to round (Dia 3-15 µm) Reproduce
  by budding BudBlastospore
• Pseudohyphae
• Macr. Pasty colonies (resemble bacteria)

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MOULD

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

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Mould-Definitions

• Hypha
• Mycelium a. Vegetative
• b. Aerial

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Classification of Hyphae

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

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DIMORPHIC

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

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Subcellular Structure of Fungi

• Capsule (present only in some fungi)
• Cell wall
• Cell membrane
• Cytoplasm
• Nucleus, nuclear membrane, nucleolus, ER,
  mitochondria, vacuoles

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CAPSULE

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

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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

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Major polysaccharides of fungal cell wall

• POLYMER MONOMER
• 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.

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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

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FUNGAL SPORES

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

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SEXUAL SPORES

• 1. Zygospore
• 2. Ascospore
• 3. Basidiospore
• 4. Oospore

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ASEXUAL SPORES

• 1. Arthrospore
• 2. Blastospore
• 3. Chlamydospore
• 4. Macroconidium
• 5. Microconidium
• 6. Sporangiospore

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Fungi-Taxonomic classification

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

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Fungi-Taxonomic classification

• SEXUAL SPORE CLASS
• Zygospore----------Zygomycetes
• Basidiospore--------Basidiomycetes
• Ascospore----------Ascomycetes
• None/Unknown---- Deuteromycetes
• (Fungi Imperfecti)

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MYCOSES

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

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LABORATORY DIAGNOSIS OF MYCOSES

• Direct microscopic examination
• Gram, potassium hydroxide (KOH), calcofluor
  white, India ink
• Culture
• Sabouraud dextrose agar
• Mycobiotic agar
• Serology