Download General Properities of Fungi

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
Chitin
Chitosan
Cellulose
-Glucan
-Glucan
Mannan
MONOMER
N-acetyl glucosamine
D-Glucosamine
D-Glucose
D-Glucose
D-Glucose
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
Class
Order
Family
Genus
Species
-mycota
-mycetes
-ales
-ceae
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