General Properties of Fungi Sevtap Arikan, MD. FUNGUS Widely distributed in nature (air, water,...

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

•MulticellularMicr.: Hypha(e) (dia: 2-10 µm)

SporesMacr.: 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 NonseptateB. 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

CAPSULEStructure: Polysaccharide Functions: -Antiphagocytic

-Virulence factor

•Exist only in some fungiCryptococcus neoformans (encapsulated yeast)

CELL WALL• Antigenic in natureStructure: 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 MONOMERChitin N-acetyl glucosamineChitosan D-GlucosamineCellulose D-Glucose-Glucan D-Glucose-Glucan D-GlucoseMannan D-Mannose

• The type and amount of the polysaccharide vary from one fungal species to other.

CELLULAR MEMBRANEStructure: BilayeredPhospholipidsSterols (ergosterol, zymosterol)

Functions: a. Protects cytoplasmb. regulates the intake and secretion of

solutesc. 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. Arthrospore2. Blastospore3. Chlamydospore4. Macroconidium5. Microconidium6. Sporangiospore

Fungi-Taxonomic classification

• Depends primarily on the type of sexual spore

Phylum -mycotaClass -mycetesOrder -alesFamily -ceaeGenusSpecies

Fungi-Taxonomic classification

SEXUAL SPORE CLASSZygospore----------ZygomycetesBasidiospore--------BasidiomycetesAscospore----------AscomycetesNone/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