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Ch 12

Ch 12. The Eukaryotes: Fungi Algae Protozoa Helminths. Student Learning Outcomes. List the defining characteristics of fungi. Identify two beneficial and two harmful effects of fungi. List the defining characteristics of protozoa.

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Ch 12

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  1. Ch 12 The Eukaryotes: Fungi Algae Protozoa Helminths

  2. Student Learning Outcomes • List the defining characteristics of fungi. • Identify two beneficial and two harmful effects of fungi. • List the defining characteristics of protozoa. • Differentiate an intermediate host from a definitive host. • List the distinguishing characteristics of the two classes of parasitic helminths, and give an example of each. • Provide a rationale for the elaborate life cycles of parasitic worms. • Define arthropod vector. • Differentiate between a tick and a mosquito, and name a disease transmitted by each.

  3. FUNGI • Chemoheterotroph, aerobic (molds) or facultativelyanaerobic (yeasts) • Mycology: Study of fungi • Most decomposers, few parasites of plants and animals • # of serious fungal infections increasing

  4. Characteristics Hyphae: Cell filaments, mostly septate Mycelium: Mass of hyphae Molds: mostly filamentous Yeasts: non-filamentous, unicellular fungi Budding yeasts divide asymmetrically. Dimorphic fungi: yeast-like at 37C, mold-like at 25C. Fungal spores are reproductive spores (unlike bacterial spores). Used to differentiate fungi. Growth in acidic, low-moisture, high osmotic pressure environments.

  5. Economic Effects of Fungi p. 341 The good: • Saccharomycescerevisiae: Bread, wine, HBV vaccine • Trichoderma: Cellulase for clear fruit juice • Taxomyces: Taxol • Entomophaga: Biocontrol • Paecilomyces: Kills termites The bad: • Mold spoilage The ugly:

  6. Fungal Diseases – Mycoses p. 335 • Systemic mycosis: infection deep within body, affects many tissues and organs. Histoplasmosis and coccidiomycosis. • Subcutaneous mycosis: Saprophytic fungi, e.g.: Sporotrichosis. • Cutaneous mycosis = Dermatomycosis: affects keratin-containing tissues (hair, nails, skin). • Superficial mycosis: localized on hair shafts and superficial skin cells. Opportunistic mycoses: • caused by normal microbiota or fungi that are not usually pathogenic (E.g.: Candidiasis, Pneumocystis pneumonia, et.al.) • usually systemic.

  7. Human eyelash with unknown fungus infection. Minimal damage to skin or underlying tissues. However, if IS impaired, can encourage infecting fungus to proliferate.

  8. ALGAE Mostly Photoautotrophs in Ocean p. 343/44 Several forms of shellfish poisoningaffecting fish, sea mammals and humans Toxins are ingested and concentrated by shellfish (e.g.: mussels, oysters, clams, scallops) Both may produce potent marine toxins

  9. Diseases due to marine toxins • Domoic Acid Intoxication (1st reported case in Canada, 1987) Diatomes Muscles  HoDiarrhea and memory loss. Also sea lions and birds • Paralytic shellfish poisoning (PSP): Dinoflagellates of genus Alexandriumproduce saxitoxinsDiatomes Muscles/clams  Ho Red tide • Ciguaterapoisoning: DinoflagellateGambierdiscustoxicusmoves up food chain to large fish

  10. See p. 351 PROTOZOA Unicellular, eukaryotic chemoheterotrophs. Large and diverse group. Few are pathogenic. Found in soil and water and as normal microbiota in animals. Trophozoite: Vegetative form (feeding and growing). Asexual reproduction via fission, budding, or schizogony (multiple fission). Sexual reproduction via conjugation. Some protozoa can produce a cyst that provides protection during adverse environmental conditions.

  11. Some Medically Important Protozoa • Giardialamblia(G. intestinalisor G. duodenalis). In ho and mammals. Diagnosis via cysts in feces • Trichomonalvaginalis

  12. Apicomplexa: not mobile, intracellularPlasmodium , Babesia, Toxoplasma, Cryptosporidium (Clinical Focus p.355 2 3 Plasmodium vivaxLife Cycle 8 7 6 Fig 12.20

  13. Euglenozoa: HemoflagellatesTrypanosoma • Move by flagella • Hemoflagellates • Sleeping sickness • Chagas’ disease

  14. Amoebae • Move by pseudopods • Entamoebahistolyticain human GI tract. ~ 10% carriers. Amoebic disentery. • Acanthamoebain water. Can infect cornea.

  15. HELMINTHS (Parasitic Worm) • Kingdom: Animalia • Phylum: Platyhelminthes (flatworms) • Class: Trematodes (flukes) • Class: Cestodes (tapeworms) • Phylum: Nematoda (roundworms) • few are human parasites • Anatomy and life cycle modified for parasitism • Adult stage in definitive host. • Each larval stage in specific intermediate host.

  16. Life Cycle of Helminths • Monoecious (hermaphroditic) • Male and female reproductive systems in one animal • Dioecious • Separate male and female • Egg  larva(e)  adult

  17. Platyhelminths Dorsoventrally flattened • Trematode, or fluke: Leaf-shaped; suckers attaches to host tissue • Cestode, or tapeworm: Scolex (head), proglottids 4 suckers and rostellum with hooks Fig 12.27 Gravid proglottid with uterine branches

  18. Taenia solium Taenia saginata Human definitive host; pig or cattle intermediate host.

  19. Echinococcusgranulosus Fig. 12. 28

  20. Human is ….

  21. Nematodes • Roundworms have a complete digestive system • Eggs infective for humans: • Enterobiusvermicularis(pinworm). Most common worm infection in US (30% of children, 16% of adults infected) • Ascarislumbricoides: Ascariasis. 2nd most common worm infection in US. (Most common worldwide; > 1 bio infected)

  22. Pinworm / Enterobiusvermicularis Fig12.29

  23. ova Pinworm (Enterobiusvermicularis) in sigmoid colon

  24. Diagnosing Pinworm Disease Do test immediately after waking up.Several samples might need to be examined. Since scratching of the anal area is common, samples taken from under the fingernails may also contain eggs. pinworm paddle

  25. Larvae Infective for Humans Fig 25.23 Hookworms Necatoramericanusand Ancylostomaduodenale

  26. The HeartwormDirofilariaimmitis Primarily in dogs and cats  human heart failure, also in human lungs Spread via mosquitoes Fig 12.30

  27. ARTHROPODS AS VECTORS Kingdom: Animalia • Phylum: Arthropoda(exoskeleton, jointed legs, segmented body) • Class: Insecta (6 legs) • Lice, fleas, mosquitoes • Class: Arachnida (8 legs) • Mites and ticks • Arthropods that carry diseases are called vectors. • Elimination of vectorbornediseases best via control or eradication of vectors. Fig 12.32

  28. Arthropod Vectors • Mechanical transmission • Biological transmission • Microbe multiplies in vector • Definitive host • Microbe’s sexual reproduction in vector The End

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