Dr Hams M A Mohamed Assistant professor of

Dr. Hams M. A. Mohamed Assistant professor of Microbiology

Mycology (from the Greek mukē, meaning "fungus") is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for medicine (e. g. , penicillin), food (e. g. , beer, wine, cheese, edible mushrooms) and as well as their dangers, such as poisoning (mycotoxin) or infection

Fungus v. Widely distributed 100, 000 – 200, 000 species About 300 pathogenic for man v. Eukaryotic developed cellular structure v. Facultative anaerobic/strict aerobic v. Chemotropic, nutrition: by absorption v. Nonphotosynthetic, saprophytic

Special character of fungi o o o Eukaryotic – a true nucleus Do not contain chlorophyll Have cell walls Produce filamentous structures Produce spores

Classification according morphology 1 -Yeast 2 -Mould 3 -Dimorphic

YEAST STUCTURE

YEAST § Unicellular § Microscopic • • • Oval to round (Dia: 3 -15 µm) Reproduce by budding Bud = Blastospore Pseudohyphae (chains of yeast cells) § Macroscopic: Pasty colonies

Example Yeast: Candidasis Small spherical yeasts Ø Budding Ø Pseudohyphae Ø Gastrointestinal, upper Ø respiratory, and genital mucosae Most common human Ø nosocomial infection

MOULD STUCTURE

MOULD • Microscopic Multicellular • Ø Hypha(e) (surface and aerial) Ø Aerial hyphae = Spores • Macroscopic ØSurface texture: ØGlaborous/Cottony/wooly/ ØPigmentation. velvety/ granular. . .

Classification of Hyphae Existence of septa v. Septate v. Non -septate Shape and Morphology v. Racquet ; Spiral v. Nodular ; Root-like (rhizoid) v. Pectinate ; Chandler

DIMORPHIC v. Capable of growing in mould or yeast form under different environmental conditions (temperature, CO 2, nutrients) v. Thermal dimorphism (a group of pathogenic fungi)

Subcellular Structure of Fungi § Capsule (present in some fungi) § Cell wall § Cell membrane § Cytoplasm

CAPSULE Structure: Polysaccharide Functions: Antiphagocytic India Ink Preparation Cryptococcus neoformans (encapsulated yeast)

CELL WALL ØAntigenic in nature ØStructure: Multilayered o Polysaccharides (~90%) o Proteins, glycoproteins (~10%) ØFunctions: o Provides shape, rigidity, strength and protection from osmotic shock

Major polysaccharides of fungal cell wall POLYMER Chitin Chitosan Cellulose -Glucan Mannan MONOMER N-acetyl glucosamine D-Glucose D-Mannose Type & amount vary from species to species

CELLULAR MEMBRANE v. Structure: Bilayered Phospholipids Sterols (ergosterol, zymosterol) v. Functions: Protects cytoplasm Regulates intake & secretion of solutes Facilitates capsule & cell wall synthesis

Reproduction

FUNGAL SPORES Function in reproduction of fungi 1. Sexual reproduction -- Sexual spores 2. Asexual reproduction -- Asexual spores a. Sporulation b. Fragmentation c. Budding 3. Parasexual reproduction -- Genetic exchange

ASEXUAL SPORES 1 -conidia 2. Arthrospore 3. Blastospore 4. Chlamydospore

Blastospore

Aspergillus Species

Rhizopus: sporangium filled with sporangiospores.

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

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

• Zygospore-----1 -Migration of nuclei will occur in the tips of both progametangia 2 -Septa are laid down at the apex of the progametangia to form isogametangia Zygomycet

3 -Karyogamyimmediately follows to form a multinucleate zygote 4 -The zygote will form a thick, pitted wall around itself to form the zygospore

• Basidiospore---- Basidiomycetes

Ascospore----- Ascomycetes

Stages of ascus formation Ascus mother cell crozier

PATHOGENICITY OF FUNGI 1. Thermotolerance 2. Ability to survive in tissue environment 3. Ability to withstand host defenses

Predisposing Factors v. Antibiotic therapy v. Immunosuppression ØGenetic ØAcquired (agamma globulinemia; steroids) v. Infectious or other diseases (cancer) v. Wounds

Features of Fungus Infections o Not contagious; dermatophytes exception o Opportunistic o Host is predisposed and/or exposed to large number of spores o Infections are chronic with granulomatous lesions

o Cell-mediated immunity - important o Hypersensitivity response may develop o Infections are asymptomatic or selflimited

Fungal Infections Clinical Classification Superficial mycoses Subcutaneous/intermediate mycoses Systemic/deep/endemic mycoses Miscellaneous mycoses/yeasts /Opportunistic

Superficial Mycoses Chest, back, upper arm Rarely invade deeper tissue Malssezia

Cutaneous mycosis Skin, hair and nails • Dermatophytes (Microsporum, tricophyton, epidermiphyton)

Subcutaneous Mycoses Madurella v. Confined to subcutaneous tissue and rarely spread systemically. v. The causative agents are soil organisms introduced into the extremities by trauma.

Systemic Mycoses § Caused by: dimorphic fungi § histoplasma, blastomyces, coccidioides, sporothrix § Involve skin and deep viscera § May become widely disseminated § Predilection for specific organs