Lecture Notes 4.21

Lecture Notes 4.21 - 4/21/10 PROTISTS unicellular...

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4/21/10 PROTISTS unicellular eukaryotes that lack cell walls tremendous phylogenetic diversity; represent much of the diversity found in Eukarya Diplomonads two nuclei of equal size contain mitosomes lacking citric acid cycle and electron transport Giardia intestinalis – one of most common waterborne diarrheal diseases in USA Parabasalids Basal body gives support to Golgi complex Contain hydrogenosomes for anaerobic metabolism Parasites living in urogenital tract of vertebrates and invertibrates o Trichomonas vaginalis - sexually transmitted disease of humans Unique genomes, o Most parabasilid genomes lack introns o T. vaginalis genome huge for parasite (160 mbp); contains nearly 60,000 genes (2x human genome) Euglenozoans Diverse assemblage of flagellated eukaryotes w/ crystalline rod in flagella (whose function not yet known) Some parasitic, others free-living phototrophs or chemoorganotrophs Include kinetoplasts and euglenids Kinetoplasts Named for kinetoplast; mass of DNA in single large mitochondrian Live primarily in aquatic habitats and feed on bacteria Some parasites of animals o Trypanosoma : small (20 uM) crescent-shaped cells w/single flagellum that infect humans o Trypanosoma brucei – African sleeping sickness – chronic and usually fatal Grows in bloodstream and invades CNS Spread by bite of tsetse fly; grows in intestinal tract of fly and invades salivary glands and mouthparts Euglenids Nonpathogenic and phototrophic Can lose chloroplasts in dark and feed on bacteria by 1
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phagocytosos Alveolates (al vee o lets) Presence of al ve oli (al vee uh lahy)– little cavaties under the cytoplasmic membrane (for water balance?) Three phylogenetically distinct but closely related groups o Ciliates o Dinoflagellates o Apicomplexans (āp'ĭ-k ə m- plěk 's ə n) Ciliates - e.g. - Paramecium Use cilia for motility and for ingestion of food (particulate material, bacterial cells) o ingestion into food vacuole by phagocytosis Micronucleus (sexual reproduction) and macronucleus (maintenance of basic cellular functions) Many species host endosymbionts that reside in cytoplasm or in the macronucleus o e.g . - commensal ciliates of termite hindgut harbor methanogenic Archaea o Can themselves be symbiotic as rumen protist Some species animal parasites: Balantidium coli – intestinal parasite of domestic animals that can cause dysentery-like symptoms in humans Dinoflagellates Common and diverse marine and freshwater phototrophs Flagella encircling cells give spinning motion (dinos – Greek for whirling) Some free living while others symbionts of choral reefs Several species of Gonyaulax bioluminescent – luminescence stimulated by shear forces luminescent waves or ship’s wakes Red tides – caused by toxic strains of
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Lecture Notes 4.21 - 4/21/10 PROTISTS unicellular...

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