MYCOLOGY Lab no 8

Definition: Fungi are eukaryotic organisms and include the yeasts, fleshy fungi & molds which include dimorphic fungi. Yeasts are microscopic, unicellular fungi; molds are multinucleated, filamentous fungi and the fleshy fungi include mushrooms.

All fungi are chemoheterotrophs, requiring organic compounds as an energy and carbon source. They obtain nutrients by absorbing them from their environment. Most of them survive by decaying organic material and are termed saprophytes. Some are parasitic, getting their nutrients from living plants or animals.

The study of fungi is termed mycology and the diseases caused by fungi are called mycotic infections or mycoses.

Uses of fungi In general, fungi are beneficial to humans. They are involved in : 1. The decay of dead plants and animals (resulting in the recycling of nutrients in nature). 2. The manufacturing of various industrial and food products. 3. the production of many common antibiotics, 4. and may be eaten themselves for food.

Fungi Moulds Yeast Fungi Dimorphic

Classification of fungi It is classified according to morphology into: 1. Yeasts: oval or round cells that reproduce by budding e.g: Cryptococcus neoformans . Some yeasts produce chains of elongated budding cells (Pseudohyphae) e.g: Candida albicans. .

2. Filamentous fungi (Moulds): Grow as branching filaments (hyphae). Reproduce by spores e.g.: Aspergillus, Penicillium and rhizopus species

3. Dimorphic fungi: They grow either in tissue or in culture at 37 oC in yeast form but when cultures are incubated at 22 oC they appear in mould forms. e.g.: histoplasma and blastomyces.

Specific Cultivation Medium Sabaroud’s Dextrose Agar: It has acidic PH. It contains relatively high concentrations of sugars e.g; dextrose and maltose. enhanced SDA with the addition of cycloheximide, streptomycin, and penicillin to produce an excellent medium for the primary isolation of fungi. Culture of pathogenic yeasts are incubated at 37 oC

Candida albicans it is an oval budding yeast which produces pseudohyphea. It is a normal inhabitant of the mouth, vagina and intestine . It may predominate and cause super infection. It causes oral or vaginal thrush .

Candida albicans.. Laboratory diagnosis: 1. Direct microscopic examination : Gram stain that show large gram positive budding cells with pseudohyphea. 2. Culture on sabouraud’s dextrose agar : large cream colonies with yeasty odour which can be identified by Gram stain

Filamentous Fungi Structure of Filamentous Fungi: 1. Hyphae: It is a tube or filament that could be septate or non septate

Filamentous Fungi ,cont.. 2. Mycelium: Macroscopic collection of branching hyphae Divided into: * Vegetative: diffuses into the medium to absorb nutrients. * Aerial: projects above the substrate and contains spores.

Filamentous Fungi ,cont.. 3. Spores: More resistant to unfavorable environmental condition. reproductive elements produced on the aerial mycelium. produced by asexual cell division or as a result of sexual reproduction.

Filamentous Fungi ,cont.. Asexual spores could be classified according to their relation to the parent hyphae into: * Conidiospores (never enclosed in a sac) Eg. Aspergillus, Penicillium Sporangiospores (formed inside a sac “sporangium”) Eg. Mucor sp.

Filamentous Fungi Aspergillus

Aspergillus

Penicillium

Penicillium

Mucor spp.

Rhizopus

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