Fungi

1. Fungi • Overview of fungi • True multicellularity with differentiation • Strict heterotrophs • Release enzymes into environment- digestion is extracellular • Most are saprophytic • Along with bacteria, fungi are important as decomposers • Biology of fungi • Body - mass of filaments called a mycelium • Each filament is a hypha- increase surface area for absorption • Some have crosswalls between cells-septa • Nonseptate fungi lack crosswalls between cells-multinucleate

2. Fungal mycelia and hyphae • Fig. 28.23

3. Fungi cont’d. • Fungal cell structure • Cell walls contain chitin • Polymer of glucose • Each glucose has an amino group attached • Found in exoskeletons of animals • Energy reserve is glycogen like animal cells • Move toward food source by growing toward it • Hyphae can grow as much as a meter per day! https://www.youtube.com/watch?v=EDkR2HIlEbc

4. Fungi cont’d. • Fungal reproduction • Adapted to dry land - produce wind-blown spores • Haploid reproductive cell - germinates and develops into new mycelium-asexual • Sexual reproduction - conjugation of two different mating types • Designated as + and – • Dikaryonic state- in some, the + and – nuclei do not fuse for long periods of time • After fusion of nuclei, a zygote forms - undergoes meiosis • Produces haploid spores and cycle begins again

5. Dispersal of spores • Fig. 28.24

6. Bird’s Nest Mushroom

7. Fungi cont’d. • Diversity of Fungi - classified by mode of sexual reproduction 1. Zygospore fungi - Phylum Zygomycota • Saprotrophs and parasites • Rhizopus stolonifer – black bread mold is a familiar zygospore fungus • life cycle is illustrated on following slide • Note formation of a zygospore from fusion of + and - hyphae

8. Black bread mold Rhizopus stolonifer • Fig. 28.25

9. Fungi cont’d. 2. Sac fungi - Phylum Ascomycota • Sexual reproductive structure called an ascus • Asci are enclosed within an ascocarp • Ascocarp develops after fusion of + and – hyphae • Union of + and – nuclei produces and ascus • Ascus produces spores by meiosis • In asexual reproduction, the asexual spores are called conidia • Unicellular ascomycetes are often called yeasts • Unequal binary fission- called budding • Fermentation by some yeasts produces CO2 and ethanol • Used to make beer, wine, and bread

10. Sexual reproduction in sac fungi • Fig. 28.26

11. Asexual reproduction in sac fungi • Fig. 28.27

12. Fungi cont’d. 3. Club fungi- Phylum Basidiomycota • Characteristic sexual reproductive structure is called a basidium • Contained within a basidiocarp • Edible part of a mushroom is the basidiocarp • Forms after fusion of + and – hyphae • Sexual reproduction is most prominent in this group • Asexual reproduction can occur by asexual spores called conidia

13. Sexual reproduction in club fungi • Fig. 28.28

14. Fungi cont’d. 4. Imperfect fungi - Phylum Deuteromycota • Includes many familiar fungi • Aspergillis- used to make soy sauce from fermenting soy beans • Penicillium- original source of penicillin • Penicillium roquefortii and camemberti- used in making blue cheeses • Deuteromycetes always reproduce asexually • Produce conidia on aerial hyphae • Sexual stage has not been identified and may not exist

15. Blue cheese • Fig. 28.29

16. Fungi cont’d. • Environmental importance of fungi • Fungi and photosynthesizers • Lichens- associations between fungi and cyanobacteria or green algae • Efficient at acquiring nutrients and moisture-can colonize poor soil, rocky surfaces • Produce organic matter and create new soil • 3 characteristic forms- crustose, foliose, fruticose • Body of lichen has 3 layers-fungi form top and bottom layers and protect middle layer of photosynthetic cells • Protects photosynthesizer and delivers water • Photosynthesized gives the fungus nutrients

17. Lichen morphology • Fig. 28.30

18. Fungi cont’d. • Environmental aspects, cont’d. • Mycorrhizal fungi • Mutualistic relationships with plant roots • Helps plants to grow more successfully in poor soils • Fungi can live on the outside surface of roots, or it can penetrate the root tissues • Plant provides organic nutrients to the fungus • Fungus brings water and minerals to the plant • Hyphae provide lots of surface area for water absorption

19. Fungi cont’d. • Medical aspects of fungi • Fungal diseases of plants • Many enter through the stomata of the leaves or through a wound • Smuts and rusts- sac fungi that parasitize cereal crops • Fungal diseases of humans • Mycoses • Cutaneous- affect only the skin • Subcutaneous-deeper skin layers • Systemic-spread throughout the body • Many fungal diseases are acquired from the environment • Ringworm from soil fungi for example

20. Smuts and rusts • Fig. 28.31

21. Fungi cont’d. • Human fungal diseases • Tineas • Skin infections-can occur anywhere on the skin • Athlete’s foot- scaling, peeling, and itching between toes • Ringworm- redness and inflammation due to enzymes released by the fungus; extends outward in a ring-shape • Histoplasmosis • Caused by Histoplasmosis capsulatum; common in the Midwest • Carried in bird droppings • Mild flu-like symptoms, fungus lives in cells of the immune system • Healed lesions in the lungs calcify • Candidiasis • Yeast infections resulting from imbalance of normal flora

22. Human diseases caused by fungi • Fig. 28.32

23. Fungi cont’d. • Control of fungi • Fungi more closely resemble animal cells than bacteria • Makes it harder to develop antibiotics that will kill fungi and not the host • Fungi synthesize steroids differently-fungicides are directed at steroid biosynthesis