Today:

1. Today: • Review of the “Fungus-like” Protists • The REAL Fungi Reminder: Fieldtrip Monday! Wear close-toed shoes. Dress for the weather. Meet at the Administration Building at 1 pm.

2. The Absorptive Protists: A Closer Look

3. What do we know about these?? Could you draw a lifecycle??

4. The Plasmodial Slime Mold Life Cycle

5. The Dictyostelida- Cellular Slime Molds • Feeding stage consists of solitary cells functioning individually • When food is low, cells follow chemical trails to form an aggregate (pseudoplasmodium) • Cells in the aggregate maintain their membranes • Haploid organisms! • Most have no flagellated stages

6. The Dictyostelida- Cellular Slime Molds http://dictybase.org/Multimedia/development/development.html

7. The Oomycotes (Water Molds and Their Relatives)

8. Oomycota: Water Molds and Their Relatives • Includes water molds, white rusts, and downy mildews • All are heterotrophic stramenopiles (“straw hair”) • May be unicellular or consist of multi-nucleated hyphae (convergent evolution!!) • Have cell walls made of cellulose • Most are diploid dominant (unlike true fungi!) • Have biflagellated cells during their life cycle

9. White Rusts Generally parasites of terrestrial plants Flagellated zoospores infect and feed on plant tissues white pine blister rust is the pale to orange colored blisters formed on white pine stem after infection chrysanthemum with CWR

10. Downy Mildews Also typically parasites of terrestrial plants Arabidopsis thaliana - Peronospora parasitica. P. parasitica is a downy mildew pathogen belonging to the oomycetes Downey mildew on soybeans

11. Other Famous Oomycetes • Potato blight (caused Irish Famine- late 1840’s)

12. The Water Molds • Important decomposers and parasites in aquatic systems secondary Saprolegnia infection

13. Next: Thinking About Real Fungi

14. General Characteristics ??

15. General Characteristics • Mostly multicellular eukaryotes • More closely related to animals than plants! • Distinguished by their: Nutritional Mode Structural Organization Growth Reproduction

16. Nutritional Mode- Fungi • Heterotrophs • Acquire nutrients by absorption • External digestion (exoenzymes) • Makes them important decomposers! • Parasitic fungi digest and absorb tissues of host!

17. Fairy Rings WHY?? Could you draw a typical fungal body?? Try to include the following key terms: hyphae, septa, mycellium

18. Structural Organization- Fungi • Vegetative bodies usually diffusely organized within and around the food source • Except yeasts, fungi constructed of filamentous hyphae • Hyphae form an interwoven mat, a mycellium • Largest mycellium discovered is 3.4 miles in diameter!!

19. The Fungi: Structural Organization

20. Structural Organization- Fungi • Most hyphae are divided into cells by cross-walls called septa (septa have large pores!) • Some fungi are aseptate- no divisions within the hyphae. These are the Coenocytic Fungi • Parasitic fungi have modified hyphae, haustoria, specialized to penetrate the tissues of the host • Most fungal cell walls are composed of chitin

21. Structural Organization- Fungi

22. Fungal Growth • Growth is extremely rapid! (can add 1 kilometer per day of hyphae!!) • Possible because of efficient transfer of materials by cytoplasmic streaming to the tips

23. Fungal Dispersal and Reproduction • Fungi reproduce by releasing spores • Spores may be produced either sexually or asexually • A single fungus may produce trillions of spores

24. Fungal Life Cycles • Most fungal hyphae and spores are haploid • Some mycelia may form through the fusion of two genetically distinct hyphae. This mycelium is then a heterokaryon. • The distinct nuclei may remain isolated, or may mingle and even exchange chromosomes and genes via a cross-over like process.

25. Sexual Reproduction in Fungi • In sexually reproducing fungi, the union occurs in two stages: 1. Plasmogamy- fusion of the parents’ cytoplasm 2. Karyogamy- fusion of haploid nuclei of the two parents • During the time lag (minutes to centuries!) the mycelium is a heterokaryon • Occasionally the haploid nuclei pair off, two to a cell. This mycelium is dikaryotic.

26. Sexual Reproduction in Fungi You Try!

27. Fungal EvolutionAnimals and fungi from a common aquatic, flagellated, protistan ancestor?

28. Evolution of the Fungi

29. The Chytridiomycota • Mainly aquatic • May be saprobes, parasites • Form flagellated spores (zoospores)  Protists?? • Most have coenocytichyphae, some unicellular

30. Chytrids and Fungal Evolution • Chytrids are found associated with plants very early in the fossil record (408-360 million years ago) • Molecular evidence also suggests these are the most primitive fungi

31. The Zygomycota- the Zygote Fungi • Mostly terrestrial in soil or on decaying material • Distinguished by a resistant zygosporangium • Hyphae are coenocytic with septa only where reproductive cells are formed

32. You Try: Modify your generic fungal lifecycle to represent a zygomycete. Zygomycete Life Cycle

33. Famous Zygomycota • The black bread mold, Rhizopus • The dung fungus, Pilobolus

34. The Glomero-mycetes • Small but ecologically distinct group! • Form arbuscularmychorrhizae Photo: Ryan Geil

35. Evolution of the Fungi

36. The Ascomycota (Sac Fungi) • 30,000+ species from marine, freshwater, and terrestrial habitats • Unicellular yeasts to large elaborate morels! • Many live with algae as lichens, may also form mycorrhizae with plants, or between cells in leaves!

37. You Try: Modify your generic fungal lifecycle to represent an Ascomycete. Ascomycetes

38. Other Ascomycetes

39. Infamous Ascomycetes… An American Chestnut Tree with Chestnut Blight

40. The Basidiomycota- Club Fungi • ~30,000 fungi including mushrooms, shelf fungi, puffballs, and rusts & smuts • Important decomposers (lignin!), also form mycorrhiza

41. You Try: Modify your generic fungal lifecycle to represent a Basidiomycete.

42. Other Basidiomycetes

43. Wood Rot • Brown Wood Rot: Fungi eats cellulose and leaves behind brown lignin • White Wood Rot: Fungi eats brown lignin and leaves behind white cellulose • Very important to nutrient cycling!! Images: Tom Volks, University of Wisconsin

44. Evolutionarily, the Fungi are Divided into Phyla based on Reproductive Strategy

45. Ecological Adaptations in the Fungi 1. Molds- • Rapidly growing, asexually reproducing fungus • Grow as saprobes or parasites on a variety of substrates • Example: Penicillium (an ascomycete) Molds that have no known sexual stage are called imperfect fungi (deuteromycetes)

46. Ecological Adaptations in the Fungi 2. Yeasts- • Unicellular fungi in moist of liquid habitats • Reproduce asexually by simple division or budding • Includes members of the Ascomycota, Basidiomycota and Imperfect Fungi.

47. Ecological Adaptations in the Fungi 3. Lichens- Symbiotic association of millions of algae or cyanobacteria within a mesh of fungal hyphae (most commonly ascomycetes)

48. Ecological Adaptations in the Fungi 3. Lichens- Lichens absorb most of their minerals from dust or rain, making them good colonizers, but sensitive to pollutants. Lichens survive in very arid conditions, but photosynthesize only when water levels are sufficient, resulting in extremely slow growth.

49. Ecological Adaptations in the Fungi 4. Mycorrhizae- • Mutualistic associations of plant roots and fungi • Increase the absorptive surface of the plant roots • Fungus provides minerals for organic nutrients synthesized by the plant • Found in almost all vascular plants!

50. Ecological Adaptations in the Fungi 4. Mycorrhizae- Can be endo or ecto-mycorrhizae Endomycorrhizae- penetrates the cortical cells (but not the cell membrane); usually a zygomycete (ArbuscularMycorrhizal Fungi) Ectomycorrhizae- forms a sheath around the root; usually a basidiomycete