• 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)

Aspergillus
Coccidioides
Crypotococcus

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

• 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

• 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