Fungi• Mycology• Avascular, typically not motile • Aerobes or facultative anaerobes • Chemoorganoheterotrophs

– Many are saprophytes – Some are parasites

• Cell walls similar in structure to plants but vary in chemical composition– Chitin, glucan, mannan

• Thallus (body) – unicellular (yeasts) or multi-cellular (molds)

• Mycelium (molds)– loosely organized mass of filamentous hyphae

Aspergillus niger

• Dimorphic Fungi – Most serious fungal

pathogens– Grow as yeast or mold – Depends on

environmental conditions

• Fungi typically reproduce by means of spores– sexual (meiotic) and asexual (mitotic) spores may

be produced– asexual fragmentation may occur

•Spores are typically released from aerial hyphae in molds

•Vegetative hyphae are involved in nutrient absorption

• Typically wind dispersed • Commonly used to identify fungal pathogens• Two types of asexual spores:

– Sporangiospore (inside sporangium sac)– Conidiospore (Various forms, not formed in a sac)

Asexual spores

Conidiospores

Aspergillus

Coccidioides

Crypotococcus

Sporangiospores

Rhizopus

• Most yeasts reproduce asexually through budding– Form psudo-hyphae– Saccharomyces

• Fission yeasts divide evenly to produce two cells– Schizosaccharomyces

• Fungi classified into divisions (phyla) according to sexual reproductive process:– Chytridiomycota (primitive fungi)– Zygomycota (conjugation fungi)– Ascomycota (sac fungi)– Basidiomycota (club fungi)– Deuteromycota (imperfect fungi)

• anamorphic fungi

Pathogenic Fungi

• Stachybotrys – the spores are inhaled causing serious forms of

hemorrhagic pneumonia– Produce several toxic chemicals called mycotoxins

• Aspergillus – commonly grows as “mildew” in shower– can cause opportunistic infections– Inhaled soil spores can cause Aspergillosis

• Pneumocystis– severe pneumonia in AIDS patients

• Candida albicans– Causes skin level fungal infections of the mouth (oral

thrush), groin (diaper rash), and the vagina (candida vaginitis) or “yeast infection”

– Dimorphic fungi that can cause serious systemic mycoses

• Cryptococcus neoformans– cryptococcosis, one of the most serious fungal

diseases worldwide– major manifestation is meningoencephalitis – has become increasingly important with the AIDS

epidemic

Beneficial fungi

• Fungi decomposers in food webs• Most plants require association with Mycorrhizae• Many fungi are a source of food

  

               

• Saccharomyces – Fermentation of bread and alcoholic beverages

• Torulopsis – protein supplements for humans and cattle

• Aspergillus – produce citric acid for food and beverages

• Trichoderma – fruit juice production