Kingdom Protista Highly diverse group of organisms Size

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 1

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 2

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 3

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 4

5 http: //www. actionbioscience. org/evolution/figu res/dacksfig 1. gif

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 6

Some protozoal terminology 7 • 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 8 • Euglenozoa – Ameobae – Euglenoids – Kinetoplastids • Archaezoa – Diplomonadida – Parabasala http: //www. jracademy. com/~mlechn er/archive 1999/paramecium. JPG

Protozoa: details and examples 9 • 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: //cgdc 3. igmors. u-psud. fr/microbiologie/apicomplexans_fichiers/image 002. jpg 10

Alveolates continued 11 – 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. 12

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 13

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/0149. jpg 14

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/r 119. jpg

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. 16