1. Characterizing and Classifying Eukaryotes
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 Decompose dead organisms and recycle their nutrients
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