Understanding Eukaryotic Organisms: Protozoa, Fungi, Algae

1. Chapter 12 Characterizing and Classifying Eukaryotes

2. Five major groups of eukaryotic microbes: • Protozoa • Fungi • Algae • Water molds • Slime molds • Include both human pathogens and organisms vital for human life

3. General Characteristics of Eukaryotic Organisms • Reproduction in Eukaryotes • More complicated than that in prokaryotes • Eukaryotic DNA packaged with histones as chromosomes in the nucleus • Have variety of methods of asexual reproduction • Budding • Fragmentation • spore formation • Schizogony (discussed later) • Many reproduce sexually by forming gametes and zygotes • Algae, fungi, and some protozoa reproduce both sexually and asexually

4. General Characteristics of Eukaryotic Organisms • Reproduction in Eukaryotes • Nuclear division • Nucleus has one or two complete copies of genome • Single copy – haploid (most fungi, many algae, some protozoa) • Two copies – diploid (remaining fungi, algae, and protozoa) • Two types • Mitosis • Meiosis

5. Reproduction in Eukaryotes • Nuclear division • Mitosis • Begins after cell has duplicated its DNA; cell partitions replicated DNA equally between two nuclei • Maintains ploidy of parent nucleus • Four phases • Prophase • Metaphase • Anaphase • Telophase

6. Reproduction in Eukaryotes • Cytokinesis (cytoplasmic division) • Typically occurs simultaneously with telophase of mitosis • In some algae and fungi, may be postponed or not occur at all • Results in multinucleated cells called coenocytes

7. [INSERT FIGURE 12.2]

8. Shizogony-some protozoa, like Plasmodium-asexual reproduction-multiple mitosises followed then by cytokinesis [INSERT FIGURE 12.3]

9. Classification system is changing [INSERT FIGURE 12.4]

10. Protozoa • Diverse group defined by three characteristics • Eukaryotic • Unicellular • Lack a cell wall and most (but not all) are heterotrophic • Motile by means of cilia, flagella, and/or pseudopodia (except subgroup, apicomplexans) • Distribution of Protozoa • Require moist environments • Most live worldwide in ponds, streams, lakes, and oceans; critical members of plankton • Others live in moist soil, beach sand, and decaying organic matter • Very few are pathogens

11. Protozoa • Morphology of Protozoa • Characterized by great morphologic diversity • Some have two nuclei • Macronucleus contains many copies of genome – controls metabolism, growth, and sexual reproduction • Micronucleus – involved in genetic recombination, sexual reproduction, and regeneration of macronuclei • Variety in number and kinds of mitochondria • Some have contractile vacuoles – maintains osmoregulation • All aquatic pathogenic protozoa produce trophozoites • Motile feeding stage • some produce cysts • Hardy resting stage

12. Protozoa • Nutrition of Protozoa • Most are chemoheterotrophic • Obtain nutrients by phagocytizing bacteria, decaying organic matter, other protozoa, or the tissues of host • Few absorb nutrients from surrounding water • Dinoflagellates and euglenoids are photoautrophic

13. Protozoa • Reproduction in Protozoa • Most reproduce asexually only (binary fission or schizogony) • Few also have sexual reproduction

14. Protozoa [INSERT TABLE 12.2]

15. Protozoan Classification • Parabasala • Lack mitochondria • includesTrichomonas • Diplomonadida • Lack mitochondria, Golgi, peroxisomes • Includes Giardia • Euglenozoa • Euglenids – share characteristics of both plants and animals (chloroplasts and flagella) • Kinetoplastids – single mitochondria • includesTrypanosoma • Aveolates • 3 subgroups: • Apicomplexans – pathogens of animals (includes Plasmodium, Toxoplasma) • Dinoflagellates – photosynthetic but molecular data show they are more closely related to ciliates than algae • Ciliates – have cilia ( includes Vorticella, Paramecium) • Amoebae – have pseudopodia, little uniformity in this group • Rhizaria – threadlike pseudopodia – include foraminiferans, radiolarians • Amoebozoa – include amoebas • Can cause disease in eyes and brains of animals • Includes slime molds • Plasmodial – acellular, filaments of cytoplasm • Cellular slime molds

16. Protozoa [INSERT FIGURE 12.14]

17. Fungi • Chemoheterotrophic • Have cell walls typically composed of chitin • Lack chlorophyll; do not perform photosynthesis • Cytokinesis does not always happen after mitosis resulting in coenocytes (multiple nuclei) • Related to animals • The Significance of Fungi • Decompose dead organisms and recycle their nutrients • Form associations with roots of vascular plants, which help plants absorb water and minerals • Used for food and in manufacture of foods and beverages • Produce antibiotics • Serve as important research tools • 30% cause diseases of plants, animals, and humans • Can spoil fruit, pickles, jams, and jellies

18. Fungi [INSERT FIGURE 12.16]

19. Fungi • Nutrition of Fungi • Acquire nutrients by absorption • Most are saprobes (secrete enzymes into environment to degrade) • Some trap and kill microscopic soil-dwelling nematodes • Haustoria (slender projections) allow some to derive nutrients from living plants and animals • Most are aerobic; some are anaerobic; many yeasts are facultative anaerobes

20. Fungi • Reproduction in Fungi • All have some means of asexual reproduction involving mitosis and cytokinesis • Asexual spores are classified by their mode of development (the structures which they are derived from) • Most also reproduce sexually

21. Fungi • Reproduction in Fungi • Budding and asexual spore formation • Yeasts bud in manner similar to prokaryotic budding • Pseudohypha – series of buds that remain attached to one another and to parent cell

22. Fungi [INSERT FIGURE 12.19]

23. Fungi • Classification of Fungi • Division Zygomycota • Division Ascomycota • Division Basidiomycota • Deuteromycetes

27. Fungi • Classification of Fungi • Deuteromycetes • Heterogeneous collection of fungi whose sexual stages are unknown • rRNA analysis revealed that most deuteromycetes belong in the division Ascomycota

28. Fungi • Lichens • Partnerships between fungi and photosynthetic microbes (green algae or cyanobacteria) • Abundant throughout the world, particularly in pristine habitats • Grow on soil, rocks, leaves, tree bark, other lichens, and even on backs of tortoises, in almost every habitat • Occur in three basic shapes – fruticose, crusts, foliose • Important in creation of soil from rocks • Eaten by many animals

29. Fungi [INSERT FIGURE 12.26]

30. Fungi [INSERT TABLE 12.3]

31. Algae • Simple, eukaryotic, phototrophic organisms that carry out oxygenic photosynthesis using chlorophyll a • Have sexual reproductive structures; every cell becomes a gamete • Differ widely in distribution, morphology, reproduction, and biochemical traits • Distribution of Algae • Most are aquatic, living in the photic zone of fresh, brackish, and salt water • Have accessory photosynthetic pigments that trap energy of light and pass it to chlorophyll a

32. Algae • Morphology of Algae • Unicellular (phytoplankton), colonial, or have simple multicellular bodies (“seaweed”)

33. Algae • Reproduction in Algae • Asexual reproduction in unicellular algae involves mitosis followed by cytokinesis • Unicellular algae that reproduce sexually form zygotes from individual gametes; zygote undergoes meiosis • Multicellular algae may reproduce asexually by fragmentation • Many multicellular algae reproduce sexually with alternation of generations

34. Algae [INSERT TABLE 12.4]

35. Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors • Parasitic worms have microscopic infective and diagnostic stages – usually eggs or larvae • Arthropod vectors are animals that carry pathogens • Mechanical vectors • Biological vectors • Disease vectors belong to two classes of arthropod • Arachnida • Insecta

36. Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors • Arachnids • Adult arachnids have four pairs of legs • Ticks are the most important arachnid vectors • Hard ticks are most prominent tick vectors • A few mite species transmit rickettsial diseases

37. Other Eukaryotes of Microbiological Interest: Parasitic Helminths and Vectors • Insects • Adult insects have three pairs of legs and three body regions • Include • Fleas • Lice • Flies • Mosquitoes