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

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

Fungus-like Animal-like protists Water molds Slime molds 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

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

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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

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

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

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).

Apicomplexans Complex structure of organelles involved in infection. http://cgdc3.igmors.u-psud.fr/microbiologie/apicomplexans_fichiers/image002.jpg

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

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.

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

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

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 http://habitatnews.nus.edu.sg/news/chekjawa/ria/photos/r119.jpg

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.