power point presentation guide fungi.pptx

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1. Fungi

2. 23.1 High-Flying Fungi Dust carries spores of fungi long distances – even across oceans Puccinia graminis is the fungal pathogen that causes wheat stem rust, a disease that destroys food crops worldwide Plant breeding programs have developed rust-resistant strains of wheat – but a mutant form of the fungus (Ug99) is now infecting rust-resistant wheat

3. Sporangia of Wheat Stem Rust

4. Developing Fungus-Resistant Wheat

5. 23.2 Fungal Traits and Classification Fungi are heterotrophs that obtain nutrition from their environment by extracellular digestion They have walled cells, spend their lives fixed in place, and disperse by producing spores Most are free-living saprobes that live on the remains of other organisms; others live on or in other organisms

6. Ecology of Fungi Some fungi decompose organic wastes and remains, which helps recycle nutrients in ecosystems Some form beneficial partnerships with plants, photosynthetic cells (lichen), or herbivores Some are parasites or pathogens

7. Structure of Fungi Some fungi live as single cells (yeasts) Most are a multicelled (molds, mushrooms) Multicelled fungi grow as a mesh of branching filaments ( mycelium ) – each filament is one hypha

8. Multicelled Fungi

9. Hyphae In the oldest fungal lineages (chytrids, zygomycetes, and glomeromycetes) hyphae do not have cross-walls Hyphae divided into compartments by cross-walls (septae) evolved in the common ancestor of sac fungi and club fungi Cross-walls made hyphae stronger, allowing the evolution of larger, more elaborate spore-producing bodies Septate hyphae also are more resistant to desiccation than nonseptate hyphae

10. Hyphae in a Mycelium one cell (part of one hypha of the mycelium)

11. Life Cycles Asexually produced spores form by mitosis in sporangia at the tips of specialized haploid hyphae Sexual reproduction begins with cytoplasmic fusion of haploid hyphae to produce a dikaryotic stage having two genetically distinct types of nuclei ( n+n ) in each cell Fusion of two haploid nuclei produces a diploid zygote that undergoes meiosis, restoring the haploid state

12. Sexual Phase of the Fungal Life Cycle Fusion of cytoplasm dikaryotic ( n + n ) stage haploid ( n ) mycelium diploid (2 n ) zygote spores ( n ) spore-producing structure ( n ) Meiosis Fusion of nuclei

13. Phylogeny and Classification Chytrids, zygote fungi (zygomycetes), and glomeromycetes are not monophyletic groups No dikaryotic stage Few or no septae between cells of hyphae Sac fungi (ascomycetes) and club fungi (basidiomycetes) are monophyletic groups Dikaryotic mycelium Regular cross walls between cells of hyphae

14. Table 23-1 p381

15. Take-Home Message: What are characteristics of fungi? Fungi are heterotrophs that absorb nutrients from their environment Some live as single cells; others live as a multicelled mycelium They disperse by producing spores

16. 23.3 The Flagellated Fungi Chytrids are the only modern fungi with a life cycle that includes flagellated cells Some feed on organic wastes and remains Some live in guts of herbivores and help digest cellulose Some are parasites

17. A Parasitic Chytrid Frog populations are threatened by Batrachochytrium dendrobatidis, a parasitic chytrid that causes chytridiomycosis A mycosis is a disease caused by a fungus Outbreaks of B. dendrobatididis have far-reaching ecological effects because frogs help control populations of insects and serve as food for many other animals

18. Chytridiomycosis

19. Harlequin Frog

20. Take-Home Message: What are chytrids? Chytrids are fungi that produce flagellated spores Most are decomposers in soil, but some live in the animal gut, and some are parasites A parasitic species that kills amphibians is a matter of concern

21. 23.4 Zygote Fungi and Relatives Only zygote fungi (zygomycetes) produce a thick-walled diploid spore (zygospore) during sexual reproduction Zygote fungi form a branching haploid mycelium on organic material, and inside living plants and animals

22. Zygote Fungi Rhizopus species Include black bread mold, molds that spoil foods, and the fungus that causes zygomycosis Pilobolus Produces specialized spore-bearing hyphae with fluid-filled sacs that blast spores up to 2 meters

23. Figure 23-5 p382 Cytoplasmic fusion mature zygospore young zygospore between hyphae of its parents asexual reproduction gametangia mycelium spores Meiosis Fusion of nuclei Diploid ( 2n ) Haploid ( n ) Dikaryotic ( n + n )

24. 23.5 Sac Fungi—Ascomycetes Sac fungi are the most diverse fungal group Some are single cells (yeasts), but in most a haploid mycelium dominates the life cycle The hyphae have cross-walls at regular intervals and often form elaborate spore-producing bodies Sac fungi are the group that most often causes diseases in humans

25. Asexual Reproduction Sac fungi commonly reproduce by asexual mechanisms Yeasts usually reproduce asexually by binary fission or by budding Multicelled sac fungi grow as a haploid mycelium that produces spores by mitosis at the tips of specialized hyphae

26. Asexual Reproduction in Sac Fungi

27. Sexual Reproduction Two haploid hyphae undergo cytoplasmic fusion – the dikaryotic cell divides by mitosis to produce dikaryotic hyphae Dikaryotic hyphae intertwine with haploid hyphae to form a spore-producing structure called an ascocarp Spores form by meiosis inside a saclike cell called an ascus Meiosis of the ascus produces spores

28. Ascocarp: Scarlet Cup Fungus

29. Ascospores: Scarlet Cup Fungus haploid spore in ascus

30. Human Uses of Sac Fungi Food and beverages Morels and truffles Baking yeast and fermentation ( Saccharomyces, Aspergillus ), blue cheese ( Penicillium ) Drugs Antibiotics ( Penicillium , Cephalosporium ) Statins ( Aspergillus ) Natural herbicides and pesticides Arthrobotrys

31. Morels

32. Truffles

33. Take-Home Message: What are sac fungi? Sac fungi are the most diverse group of fungi; some are yeasts, but a haploid mycelium dominates most life cycles Sac fungi that reproduce sexually typically form spores inside an ascus Yeasts reproduce asexually by budding, and multicelled species by formation of conidia We use sac fungi as sources of food and beverages, as drugs, and as control agents for pests

34. 23.6 Club Fungi—Basidiomycetes Club fungi make the largest and most elaborate fruiting bodies of all fungi They are typically multicelled fungi in which a dikaryotic mycelium dominates the life cycle They form sexual spores inside club-shaped cells that develop on a fruiting body ( basidiocarp ) composed of interwoven dikaryotic hyphae

35. Figure 23-13 p386 Cytoplasmic fusion stalk gill spore ( n ) Meiosis Dikaryotic ( n + n ) stage Diploid (2 n ) stage Nuclear fusion cap Haploid ( n ) stage Hyphae of mycelium Sexual spore ( n ) at gill margin

36. Ecology and Diversity Club fungi are the only decomposers capable of breaking down lignin in plants and trees ( e.g. shelf fungus, honey mushroom) Jelly fungi form a parasitic gelatinous fruiting body that taps into the mycelia of other fungi that feed on wood Other club fungi include edible mushrooms (chanterelles, puffballs), poisonous mushrooms (death cap), and hallucinogenic psilocybin-containing mushrooms

37. Club Fungus Diversity

38. Take-Home Message: What are club fungi? Club fungi are a group of mostly multicelled fungi. Multicelled species spend most of their life cycle as a dikaryotic mycelium and have the largest, most complex spore-bearing structures of all fungi Club fungi are the only fungi that can break down lignin, and they are important in forests both as decomposers and as pathogens of trees

39. 23.7 Fungal Partners and Pathogens Fungi form partnerships with plants and with single-celled photosynthetic species Lichens Fungal endophytes Mycorrhizae Other fungi are pathogens of other species

40. Lichens A lichen is a composite organism consisting of a sac fungus and a photosynthetic cyanobacteria or green algae A lichen may be a mutualism that benefits both partners, or the fungus may be parasitically exploiting captive cells Lichens disperse by fragmentation, or the fungus alone can release spores Lichens break down rock by releasing acids, and colonize hostile such as bedrock

41. Leaflike and Pendant Lichens

42. Encrusting Lichen

43. Lichen Structure dispersal fragment (cells of fungus and of photosynthetic species) outer layer of fungal cells photosynthetic species inner layer of loosely woven hyphae outer layer of fungal cells

44. ANIMATED FIGURE: Lichens

45. Mycorrhizae Mycorrhizae are a partnership between fungi and plant roots Some hyphae form a dense net around roots but do not penetrate them (sac fungi and club fungi) Some hyphae penetrate root cells (glomeromycetes) Hyphae increase the absorptive surface area of their partner Both partners benefit Fungus concentrates nutrients for plant Plant supplies sugars to the fungus

46. young root hyphal strands A Figure 23-16a p389

47. Athlete ’ s Foot

48. Table 23-2 p391

49. Take-Home Message: What close relationships do fungi have with other species? Fungi form mutually beneficial partnerships with plants, cyanobacteria, and green algae Some ants, termites, and beetles farm fungus and rely on them for food Some fungi are pathogens that invade the tissues of plants and animals