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

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

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

Fungi- Morphological Classification Yeast Mould Dimorphic

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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