nester12 - Important Point: Chapter 12: The Eukaryotic...

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Unformatted text preview: Important Point: Chapter 12: The Eukaryotic Members of the Microbial World Three-Domain Classification “Algae” are not found in the three-domain classification scheme. Algae This is because “Algae” is not a legitimate taxonomic category. “…we will use the term algae to describe the photosynthetic members” of domain Eucarya formerly assigned to kingdom Protista. Algae are aquatic (and moist terrestrial) oxygenic phototrophs. There are both unicellular and macroscopic (and everything in between) algae. These are the Eukaryotes. All but plants will be considered in this chapter. The Green Columns are Algae Note that the algae are all over the place. It apparently is relatively simple for a eukaryote to become photosynthetic (i.e., acquisition of photosynthesis is a product of convergent evolution). The algae Gymnodinium breve and Gonyaulax spp. produce toxins that can and have harmed humans, e.g., paralytic shellfish poisoning. The Red Columns are Protozoa Note that the protozoa are also somewhat dispersed. The diversity of protozoa reflects that fact that the more primitive and therefore older eukaryotes presumably were unicellular. 1 “Protozoa” are not found in the three-domain classification scheme. This is because “Protozoa” is not a legitimate taxonomic category. This is because “Protozoa” is not a legitimate “Malaria has been one of the taxonomic category. “…we will use the term [protozoa] to describe the [non-] photosynthetic [and unicellular] members” of domain Eucarya formerly assigned to kingdom Protista. “…we will use the term [protozoa] to describe the through the ages. At least 300 [non-] photosynthetic [and unicellular] members” of million people in the world domain Eucarya formerly assigned to kingdom contract malaria each year, and Protista. Protozoa are aquatic (and moist terrestrial) mostly aerobic chemoorganotrophs. A few protozoa (e.g., Giardia spp.) lack mitochondria and consequently are fermenters. There are quite a number of diseases associated with parasitic protozoa: Trichomonas vaginalis causes vaginitis. greatest killers of humans Protozoa Protozoa “Protozoa” are not found in the three-domain classification scheme. Toxoplasma gondii causes toxoplasmosis. Plasmodium spp. causes malaria. 3 million die of it.” Protozoa are aquatic (and moist terrestrial) mostly aerobic chemoorganotrophs. A few protozoa (e.g., Giardia spp.) lack mitochondria and consequently are fermenters. There are quite a number of diseases associated with parasitic protozoa: Trichomonas vaginalis causes vaginitis. Toxoplasma gondii causes toxoplasmosis. Plasmodium spp. causes malaria. Three-Domain Classification Fungi Properties Fungi actually is a legitimate taxonomic category. Fungi are mostly chemoorganotrophic aerobes. Some yeasts are exceptional, serving as facultative aerobes, hence ethanol fermentation by brewers/bakers yeast, Saccharomyces cerivisiae. Yeasts are single-celled fungi. Molds are filamentous fungi. Macrofungi are large things like mushrooms. Fungi other than yeasts produce Hyphae which are a filamentous cellular growth. Many fungal pathogens are Dimorphic, existing as yeasts or hyphae under different circumstances. Mycelia represent a typically tangled mass of hyphae. Typically mycelia are found beneath rather than above surfaces (molds are exception). Fungi disseminate their progeny as spores (which are not equivalent to endospores). Mushrooms are above-ground fruiting bodies which disseminate the spores from extensive underground mycelia. Fungus Life Cycle Fungal Forms of Growth Though diverse, fungi are not nearly as diverse as “Protozoa,” plus note how closely related Fungi are to animals, i.e., to us. The study of Fungi is the domain of the Mycologist. 2 Fungal Ecology Fungi typically prefer drier and more acidic environments than bacteria. Fungi are crucial decomposers, especially of plant material and especially of wood. They secrete exoenzymes that digest materials extracellularly, with the digestive products then taken up into the fungal body for participation in fungal metabolism. Fungi also form important mutualistic symbioses, e.g., with plant roots as well as within algae in lichens. Fungi are important disease organisms especially of plants. However, we also harness the plant-destructive powers of fungi to produce alcoholic beverages including wine and beer. And let’s not forget baker’s years, Saccharomyces cerevisiae. Saccharomyces cerevisiae Mycoses Fungal diseases are called Mycoses. Diseases associated with fungi include: Allergic reactions to fungi or their spores (think mold spores) Ingestion of fungal toxins (think poisonous mushrooms, but also aflatoxin) Fungal infections Fungal infections, going from bad to worse, can be classified as Superficial, Intermediate, or Systemic Mycoses. Important fungal diseases include: Histoplasmosis caused by Histoplasma caapsulatum. Candida yeast infections caused by Candida albicans. Ringworm such as athlete’s foot caused by various Tinea spp. Superficial Mycosis Superficial Mycosis Fungal Growth 3 Arthropod Vectors Superficial Mycosis Superficial Mycosis Subcutaneous Mycoses Ringworm, stained preparation, macroconidia of Microsporum canis Ringworm A Mechanical Vectors carries a microbe to a new host (e.g., such as us) but the microbe does not actually replicate during this carriage. An example is Salmonella being carried by house flies. A Biological Vectors carries the microbe through some aspect of its (the microbe’s) life cycle. The assumption is that there has been some degree of adaptation between vector’s and the microbe’s lineage (i.e., among their ancestors). An arthropod is a terrestrial animal with exoskeleton and jointed appendages (e.g., legs). Included among the arthropods are: Insects (including fleas and lice). Arachnids (including ticks as well as spiders). Body & Crab Lice A Flea 4 Tapeworm Life Cycle Pinworm Life Cycle Pinworms on Perianal Folds Schistosoma japonicum (a fluke) Arthropod Vectors Helminths 5 Schistosoma japonicum (a fluke) Schistosoma japonicum (a fluke) If you like life cycles, I’ve got plenty more at www.phage.org/lectures/black11.ppt ☺ Enjoy! ☺ Link to Next Presentation 6 Helminths 12 ...
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This note was uploaded on 06/03/2011 for the course MCB 205 taught by Professor Abedon during the Spring '11 term at Ohio State.

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