The Need for Fungi

• Ecologically important decomposers• Break down complex organic molecules into simple

molecules that can be used by other organisms

Classification, Structure, and Growth of Fungi

• Yeasts• Molds• Hypha• Mycelium• Mycology• Mycosis

Figure 8.2: A false-colored SEM of Cladosporium cladosporioides, one of the most common fungi isolated from air samples (x300)

© Dr. Dennis Kunkel/Visuals Unlimited

Classification, Structure, and Growth of Fungi

• Structure of fungi– Nuclei– Many fungi form spores– No chlorophyll– Reproduce sexually and asexually– Cell walls

• Contain chitin

• Septa

Classification, Structure, and Growth of Fungi

• Nutrition in fungi– Heterotrophic

• Digestive enzymes secreted outside cell

• Brokendown products are then absorbed by cell

– Some fungi can make enzymes that very few organisms make.• Cellulase

• Ligninase

– Glucose stored as glycogen• What other organism store carbohydrates as glycogen?

– Some fungi exist as saprobes– Some fungi exist as parasites

Classification, Structure, and Growth of Fungi

• Nutrition in fungi– Usually exist in acidic conditions– Therefore fungi can grow in familiar acidic foods

• Sour cream

• Yogurt

• Citrus fruit

• Most vegetables

• Bread

• Cheese

– Favorable contamination• Cheese (e.g., blue cheese and Penicillium requeforti)

Classification, Structure, and Growth of Fungi

Reproduction in fungi– Asexual reproduction forms spores

• Hyphal fragmentation

– Arthospores

– Chlamydospores

• Mitosis – cell division where one parent cell results in two identical daughter cells that become spores

– Spores» Most are formed on sporangium or conidiophore» Conidia are spores formed unprotected at the tip of a conidiophore.» Environmentally stable, like bacterial spores» Produces extremely large number of spores» All spores are genetically identical to parent cell

Classification, Structure, and Growth of Fungi

Reproduction in fungi– Sexual reproduction

• Cell fusion and and spore formation

• Haploid parent cells (1n)

• Diploid progeny, called zygote (2n)

• Meiosis of zygote creates haploid spores (1n)

• Spores are environmentally resistant, like bacterial spores

• Spores germinate to form new haploid organism

• Results in fewer spores, but more genetic diversity when compared to asexual reproduction

Classification, Structure, and Growth of Fungi: Sexual Reproduction in Fungi

Figure 8.5: Sexual Reproduction in Fungi

Reproduced by permission of the National Research Council of Canada; O'Donnell, K.L., Ellis, J.J, Hesseltine, C.W. and Hooper, G.R. The Canadian Journal of Botany, 55(6): 662-675.

Divisions of Fungi

• Zygomycota• Ascomycota• Basidiomycota• Deuteromycota

Divisions of Fungi

• Zygomycota– Called zygomycetes– Zygospores

• Thick-walled, environmentally resistant spores

• Develop from fusion of two sexually opposite cells

– Rhizopus stolonifer: common black bread mold– Fermentation of rice into sake by one Rhizopus species– Cortisone production by different Rhizopus species

Divisions of Fungi

• Asomycota– 30,000 species of ascomycetes (a.k.a., sac fungi)– Produce Asci – spore containing sacs– Most are filamentous– Some are yeasts– Septa allow mixing of adjacent cells’ cytoplasm– Ascospores – sexually produced

Figure 8.6: Ascospores (A) and conidia (B) of the fungus Aspergillus quadrilineatus

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Divisions of Fungi

• Ascomycota– Various Penicillium species

• Antibiotics– Penicillin– Ampicillin– Amoxicillin– Methicillin

• Blue cheese

– Various Aspergillus species• Contaminate house dust• Cause allergies, respiratory illness• Aflatoxins• Production of food products

– Citric acid– Soy sauce– Vinegar– Beano

–Claviceps purpurae-Infects rye-Ingestion results in ergot disease in humans-Potential headache cure, in low doses-Potential bioterrorism weapon