Eukaryotic Microorganisms Algae and Protozoans 2

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Eukaryotic Microorganisms Algae and Protozoans 2 Eukaryotic Microorganisms . prominent members of ecosystems . useful as model systems and industry . some are major human pathogens . two groups . protists . fungi 3 Kingdom Protista . Algae - eukaryotic organisms, usually unicellular and colonial, that photosynthesize with chlorophyll a . Protozoa - unicellular eukaryotes that lack tissues and share similarities in cell structure, nutrition, life cycle, and biochemistry 4 Algae .Photosynthetic organisms .Microscopic forms are unicellular, colonial, filamentous .Macroscopic forms are colonial and multicellular .Contain chloroplasts with chlorophyll and other pigments .Cell wall .May or may not have flagella 5 6 Algae .Most are free-living in fresh and marine water – plankton .Provide basis of food web in most aquatic habitats .Produce large proportion of atmospheric O2 .Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms .Classified according to types of pigments and cell wall .Used for cosmetics, food, and medical products 7 Protozoa Protozoa 9 .Diverse group of 65,000 species .Vary in shape, lack a cell wall .Most are unicellular; colonies are rare .Most are harmless, free-living in a moist habitat .Some are animal parasites and can be spread by insect vectors .All are heterotrophic – lack chloroplasts .Cytoplasm divided into ectoplasm and endoplasm .Feed by engulfing other microbes and organic matter Protozoa 10 .Most have locomotor structures – flagella, cilia, or pseudopods .Exist as trophozoite – motile feeding stage .Many can enter into a dormant resting stage when conditions are unfavorable for growth and feeding – cyst .All reproduce asexually, mitosis or multiple fission; many also reproduce sexually – conjugation Figure 5.27 11 Protozoan Identification 12 . Classification is difficult because of diversity . Simple grouping is based on method of motility, reproduction, and life cycle 1. Mastigophora – primarily flagellar motility, some flagellar and amoeboid; sexual reproduction 2. Sarcodina – primarily amoeba; asexual by fission; most are free-living 3. Ciliophora – cilia; trophozoites and cysts; most are free-living, harmless 4. Apicomplexa – motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic Figure 5.28 13 Figure 5.32 14 Figure 5.29 15 Figure 5.30 16 17 Figure 5.31 18 Important Protozoan Pathogens 19 . Pathogenic flagellates . Trypanosomes – Trypanosoma .T. brucei – African sleeping sickness .T. cruzi – Chaga’s disease; South America . Infective amoebas . Entamoeba histolytica – amebic dysentery; worldwide Figure 5.33 20 21 .

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