Kingdom Protista

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 http://www.bhikku.net/archives/03/img/diatoms.JPG www.enviroliteracy.org/ article.php/534.html

3. Fungus-like • Water molds • Slime molds Animal-like protists Capable of ingesting their food. Found among many different groups, so not good for taxonomy. http://en.wikipedia.org/wiki/Slime_mold http://ar.geocities.com/seti_argentina/estamos_solos/ameba.jpg

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

5. http://www.actionbioscience.org/evolution/figures/dacksfig1.gifhttp://www.actionbioscience.org/evolution/figures/dacksfig1.gif

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 http://www.jracademy.com/~mlechner/archive1999/paramecium.JPG

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. http://cgdc3.igmors.u-psud.fr/microbiologie/apicomplexans_fichiers/image002.jpg

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 • 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 http://www.mhhe.com/socscience/sex/common/ibank/ibank/0149.jpg

15. Algae • Green algae • 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 http://habitatnews.nus.edu.sg/news/chekjawa/ria/photos/r119.jpg

16. Water Molds and Slime Molds • Water 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.