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Chapter 12: The Eukaryotic Members of the Microbial World. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!. Three-Domain Classification.
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Important Point: If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!
Three-Domain Classification These are the Eukaryotes. All but plants will be considered in this chapter.
“Algae” are not found in the three-domain classification scheme. • 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. • The algaeGymnodinium breve and Gonyaulax spp.produce toxins that can and have harmed humans, e.g., paralytic shellfish poisoning. Algae
The Green Columns are Algae It apparently is relatively simple for a eukaryote to become photosynthetic (i.e., acquisition of photosynthesis is a product of convergent evolution). Note that the algae are all over the place.
The Red Columns are Protozoa The diversity of protozoa reflects that fact that the more primitive and therefore older eukaryotes presumably were unicellular. Note that the protozoa are also somewhat dispersed.
“Protozoa” are not found in the three-domain classification scheme. • This is because “Protozoa” is not a legitimate taxonomic category. • “…we will use the term [protozoa] to describe the [non-] photosynthetic [and unicellular] members” of domain Eucarya formerly assigned to kingdom 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. • Toxoplasma gondii causes toxoplasmosis. • Plasmodium spp. causes malaria. Protozoa
“Protozoa” are not found in the three-domain classification scheme. • This is because “Protozoa” is not a legitimate taxonomic category. • “…we will use the term [protozoa] to describe the [non-] photosynthetic [and unicellular] members” of domain Eucarya formerly assigned to kingdom 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. • Toxoplasma gondii causes toxoplasmosis. • Plasmodium spp. causes malaria. Protozoa “Malaria has been one of the greatest killers of humans through the ages.At least 300 million people in the world contract malaria each year,and 3 million die of it.”
Three-Domain Classification Though diverse, fungi are not nearly as diverse as “Protozoa,” plus note how closely related Fungi are to animals, i.e., to us.
Fungi Properties • Fungi actually is a legitimate taxonomic category. • The study of Fungi is the domain of the Mycologist. • 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. Fungal Forms of Growth
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. Fungal Ecology
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 Histoplasmacaapsulatum. • Candida yeast infections caused by Candida albicans. • Ringworm such as athlete’s foot caused by various Tinea spp. Mycoses
Superficial Mycosis Ringworm, stained preparation, macroconidia of Microsporum canis
Superficial Mycosis 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). Arthropod Vectors
Schistosoma japonicum (a fluke) If you like life cycles, I’ve got plenty more at www.phage.org/lectures/black11.ppt Enjoy!
