Mycology ,diseases caused by fungi

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Lectures prepared by Christine L. Case
The
Eukaryotes:
Fungi

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FUNGI
 Mycology: Study of fungi
 Chemoheterotrophs, aerobic
(molds) or facultatively
anaerobic (yeasts)
 Most fungi decomposers, few
are parasites of plants and
animals
 # of serious fungal infections
increasing

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 Hyphae: Filaments of cells,
mostly septate or non-septate
 Mycelium: Mass of hyphae.
 Molds: mostly filamentous.
 Yeasts: non-filamentous, unicellular fungi.
 Budding yeasts divide asymmetrically.
 Dimorphic fungi: yeasts like 37C, molds 25C.
 Fungal spores differ from bacterial spores. Form from
aerial hyphae.
 Growth in acidic, low-moisture, high osmotic pressure
environments.
 Metabolize complex carbohydrates (e.g. lignin).
Characteristics of Fungi

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Reproduction
 Filamentous fungi can reproduce asexually by
fragmentation of their hyphae.
 In addition, both sexual and asexual reproduction in
fungi occurs by the formation of spores.
 In fact, fungi are usually identified by spore type.
 Asexual spores are formed by the hyphae of one
organism.
1) Conidiospore
2) Arthroconidia
3) Blastoconidia
4) Sporangiospore

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 Sexual spores result from the fusion of nuclei from
two opposite mating strains of the same species of
fungus.
 Fungi produce sexual spores less frequently than
asexual spores.
1) Zygospore
2) Ascospore
3) Basidiospores

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Medically Important Phyla of Fungi
1) Zygomycota, are saprophytic molds that have
coenocytic hyphae. Example: Rhizopus stolonifer,
the common black bread mold.
2) Ascomycota, or sac fungi, include molds with
septate hyphae and some yeasts. Talaromyces
3) Basidiomycota, or dub fungi, also possess septate
hyphae. Mushrooms

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Zygomycete Life Cycle

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Fungal Diseases – Mycoses
1. Systemic mycosis: infection deep within body,
affects many tissues and organs. Histoplasmosis and
coccidiomycosis.
2. Subcutaneous mycosis: Saprophytic fungi, e.g.:
Sporotrichosis.
3. Cutaneous mycosis = Dermatomycosis: affects
keratin-containing tissues (hair, nails, skin).
4. Superficial mycosis: localized on hair shafts and
superficial skin cells.
Opportunistic mycoses:
 caused by normal microbiota or fungi that are not
usually pathogenic (e.g. Candidiasis)
 usually systemic.