1. Kingdom Protista Highly diverse group of organisms
Size range from 5 µm to several meters (kelp)
Defined more by what they aren’t
Nutrient/energy acquisition ranges from photosynthesis to predatory to detrivores
Important in many food webs
Provide link between bacteria and larger organisms
library.thinkquest.org/ 12413/protist.html

2. Plant-like Protists Contain chloroplasts Representatives
Diatoms (right).
Diatomaceous earth = fossilized diatoms: abrasives and slug repellants.
Red, brown, yellow algae
Seaweed, source of agar
Dinoflagellates
Neurotoxins and red tide
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3. Fungus-like Animal-like protists Water molds Slime molds
Capable of ingesting their food.
Found among many different groups, so not good for taxonomy.

4. How to classify?
Cell ultrastructure and molecular analysis becoming the main methods used for classification.
Suggests that several kingdoms would be appropriate.
Alternative scheme, keep the kingdom Protista, classify protozoa into several phyla
Typical textbook:
4 groups of protozoa
Algae
Slime molds
Water molds

6. Protozoa What are the characteristics of Protozoa?
Unicellular eukaryotes
Lack a cell wall
Require moist environments (water, damp soil, etc)
Great amounts of diversity
Locomotion: float, cilia, flagella, pseudopodia
Nutrition: chemoheterotrophs, photoautotrophs, either
Simple to complex life cycles, reproduction
Different cell organelles, some lack mitochondria

7. Some protozoal terminology
Cyst: a resting stage similar to a spore with a thick wall and low level of metabolism.
Trophozoite: stage in life cycle during which the microbe is feeding and growing.
Merozoite: Small cells with a single nuclei produced during schizogony.
Large, multinucleated cell undergoes cytokinesis to produce multiple daughter cells (merozoites)
Cytoplasmic streaming.
Cytoskeleton aids extension of cell membrane

8. Classification of Protozoa
Alveolates
Ciliates
Apicomplexans
Dinoflagellates
Amoebae
Shelled and unshelled
Euglenozoa
Ameobae
Euglenoids
Kinetoplastids
Archaezoa
Diplomonadida
Parabasala

9. Protozoa: details and examples
Alveolates
Possess alveoli: small membrane-bound cavities of unknown function (classification by ultrastructure)
Ciliates: move by cilia, short flagella-like appendages
Includes disease-causing Balantidium
Apicomplexans: have a complex of specialized organelles at the apices (corners, tips) of the cells
Generally have complex life cycles
Include Plasmodium (malaria), Toxoplasma (toxoplasmosis).

10. Apicomplexans Complex structure of organelles involved in infection.

11. Alveolates continued Dinoflagellates
Large group of plantlike protozoa, have photosynthetic pigments (chlorophylls), cellulosic cell walls, store sugars as starch.
RNA sequences show relationship to other aveolates, not to plants.
Large portion of fresh water and marine plankton
Some encased in silica
Some bioluminescent or produce red pigments
Some produce dangerous neurotoxins

12. Amoebae Amoebae have 2 main characteristics
Move and feed using pseudopodia
Cytoskeleton aids extension of cell membrane, cytoplasmic streaming.
Lack mitochondria
Some have loose shells; some form cysts.
Fossilized shells major component in some limestones.
Some “ameobae” are classified in another group.
Entamoeba: example of disease-causing amoeba.

13. Euglenozoa Amoebae: move by pseudopodia
United by similar RNA sequences
Not particularly similar otherwise. Have mitochondria.
Amoebae: move by pseudopodia
Including disease-causing Naegleria and Acanthameoba
Euglenoids: Euglena and similar microbes
Photoautrophs, but: no cell walls, motile by flagella and other means, store paramylon instead of starch, and can grow heterotrophically in the dark. Not plants!
Kinetoplastids: mitochondrial DNA forms kinetoplast
Includes Trypanosma, a pathogen

14. Archaezoa Lack mitochondria and some other organelles
Thought to be old, hence the name (“Archae-”)
But have mitochondrial genes in nucleus.
Diplomonadida: 2 nuclei plus flagella
Includes pathogen Giardia, forms cysts, causes diarrhea
Parabasala: Single nucleus plus parabasal body.
Wood digesting microbe of termite gut.
Trichomonas,
inhabits vagina, potential STD

15. Algae Green algae Red algae Chrysophyta (golden algae, diatoms, etc)
Ancestors of plants
Red algae
Mostly marine
Source of food thickeners carrageenan and agar
Chrysophyta (golden algae, diatoms, etc)
Diatoms: major component of phytoplankton
Diatomaceous earth as abrasives, gardening tools
Brown algae
Common seaweeds, kelps

16. Water Molds and Slime Molds
Similar to fungi except for 4 major differences;
2 of 4: cellulose, not chitin in cell wall; motile spores
Phytophthora: Irish potato blight, sudden oak death
Slime molds
Acellular slime molds: The Blob, giant multi-nucleated cell; reproduces into amoebae that are amphibious
Cellular slime molds, e.g. Dictyostelium: unicellular, aggregate into slug-like structure, model for primitive development and differentiation.