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Chapter 12

Chapter 12. The Eukaryotes: Fungi, Algae, Protozoa, and Helminths. Q&A.

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Chapter 12

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  1. Chapter 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

  2. Q&A • During the Great Irish Famine of the mid–nineteenth century, well over 1 million people died or were displaced because of the devastating effects of Phytophthora infestans, an alga that infects potato crops. What damage is Phytophthora causing in other parts of the world today?

  3. Fungi Learning Objectives • 12-1 List the defining characteristics of fungi. • 12-2 Differentiate asexual from sexual reproduction, and describe each of these processes in fungi. • 12-3 List the defining characteristics of the three phyla of fungi described in this chapter. • 12-4 Identify two beneficial and two harmful effects of fungi.

  4. Fungi Mycology is the study of fungi

  5. Table 12.2

  6. Molds • The fungal thallus consists of hyphae; a mass of hyphae is a mycelium. Figure 12.2

  7. Yeasts • Unicellular fungi • Fission yeasts divide symmetrically • Budding yeasts divide asymmetrically Figure 12.3

  8. Vegetative Growth Figure 12.1

  9. Fungal Dimorphism • Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C Figure 12.4

  10. Asexual Reproduction • Conidia or conidiospores Figure 12.5a

  11. Asexual Reproduction • Arthroconidia Figure 12.5b

  12. Asexual Reproduction • Blastoconidia Figure 12.5c

  13. Asexual Reproduction • Chlamydoconidia Figure 12.5d

  14. Asexual Reproduction • Sporangiospores Figure 12.5e

  15. Sexual Reproduction • Three phases: • Plasmogamy: Haploid donor cell nucleus (+) penetrates cytoplasm of recipient cell (–) • Karyogamy: + and – nuclei fuse • Meiosis: Diploid nucleus produces haploid nuclei (sexual spores)

  16. Sexual Spores • Zygospore: Fusion of haploid cells produces one zygospore Figure 12.6

  17. Sexual Spores • Ascospore: Formed in a sac (ascus). Figure 12.7

  18. Sexual Spores • Basidiospore: Formed externally on a pedestal (basidium) Figure 12.8

  19. Medically Important Phyla of Fungi • Zygomycota • Ascomycota • Anamorphs • Basidiomycota

  20. Zygomycota • Conjugation fungi • Coenocytic • Produce sporangiospores and zygospores • Rhizopus, Mucor (opportunistic, systemic mycoses)

  21. The Life Cycle of a Zygomycete Figure 12.6

  22. Ascomycota • Sac fungi • Septate • Teleomorphic fungi • Produce sexual and asexual spores • Ascospores and frequently conidiospores • Aspergillus (opportunistic, systemic mycosis) • Blastomyces dermatitidis, Histoplasma capsulatum (systemic mycoses) • Microsporum, Trichophyton (cutaneous mycoses)

  23. The Life Cycle of an Ascomycete Figure 12.7

  24. Anamorphs • Produce asexual spores only • rRNA sequencing places most in Ascomycota; a few are Basidiomycota • Penicillium • Sporothrix (subcutaneous mycosis) • Stachybotrys, Coccidioides, Pneumocystis (systemic mycoses) • Candida albicans (cutaneous mycoses)

  25. Basidiomycota • Club fungi • Septate • Produce basidiospores and sometimes conidiospores • Cryptococcus neoformans (systemic mycosis)

  26. The Life Cycle of a Basidiomycete Figure 12.8

  27. Economic Effects of Fungi • Saccharomyces cerevisiae: Bread, wine, HBV vaccine • Trichoderma: Cellulase • Taxomyces: Taxol • Entomophaga: Biocontrol • Paecilomyces: Kills termites

  28. Fungal Diseases (Mycoses) • Systemic mycoses: Deep within body • Subcutaneous mycoses: Beneath the skin • Cutaneous mycoses: Affect hair, skin, and nails • Superficial mycoses: Localized, e.g., hair shafts • Opportunistic mycoses: Caused by normal microbiota or environmental fungi

  29. Assume you isolated a single-celled organism that has a cell wall. How would you determine that it is a fungus and not a bacterium? 12-1 • Contrast the mechanism of conidiospore and ascospore formation. 12-2 • List the asexual and sexual spores made by Zygomycetes, Ascomycetes, and Basidiomycetes. 12-3 • Are yeasts beneficial or harmful? 12-4

  30. Lichens Learning Objectives • 12-5 List the distinguishing characteristics of lichens, and describe their nutritional needs. • 12-6 Describe the roles of the fungus and the alga in a lichen.

  31. Lichens • Mutualistic combination of an alga (or cyanobacterium) and fungus • Alga produces and secretes carbohydrates; fungus provides holdfast

  32. Three Types of Lichens Figure 12.9a

  33. Lichen Thallus Figure 12.9b

  34. Economic Effects of Lichens • Dyes • Antimicrobial (Usnea) • Litmus

  35. What is the role of lichens in nature? 12-5 • What is the role of the fungus in a lichen? 12-6

  36. Algae Learning Objectives • 12-7 List the defining characteristics of algae. • 12-8 List the outstanding characteristics of the five phyla of algae discussed in this chapter. • 12-9 Identify two beneficial and two harmful effects of algae.

  37. Algae

  38. Algal Habitats Figure 12.10a

  39. Brown Alga Figure 12.11b

  40. Phaeophyta • Brown algae (kelp) • Cellulose and alginic acid cell walls • Multicellular • Chlorophyll a and c, xanthophylls • Store carbohydrates • Harvested for algin Figure 12.10b

  41. Rhodophyta • Red algae • Cellulose cell walls • Most are multicellular • Chlorophyll a and d, phycobiliproteins • Store glucose polymer • Harvested for agar and carrageenan Figure 12.10c

  42. Chlorophyta • Green algae • Cellulose cell walls • Unicellular or multicellular • Chlorophyll a and b • Store glucose polymer • Gave rise to plants Figure 12.11a

  43. Diatoms • Pectin and silica cell walls • Unicellular • Chlorophyll a and c, carotene, xanthophylls • Store oil • Fossilized diatoms formed oil • Produce domoic acid

  44. Diatoms Figure 12.12a

  45. Asexual Reproduction of a Diatom Figure 12.12b

  46. Dinoflagellates • Cellulose in plasma membrane • Unicellular • Chlorophyll a and c, carotene, xanthins • Store starch • Some are symbionts in marine animals • Neurotoxins cause paralytic shellfish poisoning Figure 12.13

  47. Oomycota • Water molds • Cellulose cell walls • Multicellular • Chemoheterotrophic • Produce zoospores Figure 12.14

  48. Oomycota Figure 12.14

  49. Oomycota • Decomposers and plant parasites • Phytophthora infestans responsible for Irish potato blight • P. cinnamoni infects Eucalyptus • P. ramorum causes sudden oak death Figure 12.14

  50. Q&A • During the Great Irish Famine of the mid-nineteenth century, well over 1 million people died or were displaced because of the devastating effects of Phytophthora infestans, an alga that infects potato crops. What damage is Phytophthora causing in other parts of the world today?

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