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Eukaryotic Microbial Diversity Overview of taxonomy. Early attempts at taxonomy: all plants and animals Some still refer to bacteria as “flora” Whitaker scheme (late 20th century) Five kingdoms: Monera (bacteria) and 4 eukaryotic kingdoms Carl Woese’s work on rRNA

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Eukaryotic microbial diversity overview of taxonomy
Eukaryotic Microbial DiversityOverview of taxonomy

  • Early attempts at taxonomy: all plants and animals

    • Some still refer to bacteria as “flora”

  • Whitaker scheme (late 20th century)

    • Five kingdoms: Monera (bacteria) and 4 eukaryotic kingdoms

  • Carl Woese’s work on rRNA

    • Three Domains: Archaebacteria, Eubacteria, and Eukaryotes

  • The four eukaryotic kngdoms:

    • Animals, plants, fungi, and protists

      • Grouped by similar structure, physiology, and behavior

      • The boundaries of these kingdoms now being altered by research in molecular biology.

  • Eukaryotes vs prokaryotes
    Eukaryotes vs. prokaryotes

    • Eukaryotes are larger

    • Eukaryotes have membrane-bound organelles

      • Nucleus, mitochondria, membrane systems

      • Larger size requires functional compartments

      • Mitochondria once bacteria? So same size!

    Microbial eukaryotes
    Microbial eukaryotes

    • Animals

      • Parasitic worms; studied by Parasitologists

    • Fungi

      • Yeasts and molds, studied by Mycologists

      • Several types can cause human disease

    • Protists

      • Unicellular eukaryotes with many different characteristics. Also studied by Parasitologists.

      • Some cause human disease

    • Plants: not of particular interest other than hosts

    Protista the grab bag kingdom
    Protista: the grab bag Kingdom

    • Protists are generally microscopic, unicellular, eukaryotes.

      • Historically, classified together because of their differences from other organisms

      • Always recognized as a highly diverse group

    • Since the application of molecular biology, taxonomy of all things constantly changing.

      • In new schemes, Protista split into 7 kingdoms, they are that different from one another and from other organisms

    Kingdom protista
    Kingdom Protista

    • Highly diverse group of organisms

      • Size range from 5 µm to 5 mm

      • 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

    • Learn simple, unofficial taxonomy 12413/protist.html

    Plant like protists
    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 article.php/534.html

    Fungus like

    • Water molds

      • Motile spores, unlike true fungi

      • Phytophora infestans: caused the great Irish potato blight and extensive emigration.

    • Slime molds

      • Cellular slime mold, individual amoebas that aggregate to form fruiting body

      • Plasmodial slime mold: the blob. Similar life cycle.

    The protozoa
    The Protozoa

    • Most medically important protists are protozoa

      • Unicellular eukaryotes

      • Lack a cell wall

      • Require moist environments (water, damp soil, etc)

      • Mostly Animal-like

    • 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

    Animal like protists
    Animal-like protists

    • Most likely to cause human disease

    • Typically have a complex life cycle

      • Esp. sporozoans, involving several stages and multiple hosts

    • Classified mostly according to type of motility

      • Amoebas (cytoplasmic streaming)

      • Ciliates (cilia)

      • Flagellates (flagella)

      • Sporozoans (non-motile)


    • Amoebae move and feed using pseudopodia

      • Cytoskeleton aids extension of cell membrane, cytoplasmic streaming.

  • Some have loose shells; some form cysts.

    • Fossilized shells major component in some limestones.

  • Protists with the structure of “ameobae” are classified in more than one group.

  • Most live in the environment, eating bacteria

    • Entamoeba, Naegleria : examples of disease-causing amoebae.

  • Other protozoa
    Other Protozoa

    • Ciliates:

      • move by cilia, short flagella-like appendages

      • Includes disease-causing Balantidium

    • Flagellates:

      • Move using flagella

      • Some disease-causing flagellates include

        • Giardia, forms cysts, causes diarrhea

        • Trichomonas, inhabits vagina, potential STD

    • Sporozoans: Generally have complex life cycles

      • Include Plasmodium (malaria), Toxoplasma (toxoplasmosis)


    • Mycology: the study of fungi

    • Fungi are mostly saprophytes, all heterotrophs

      • Saprophytes: decay non-living organic matter

        • Fungi are the kings of decomposition

      • Heterotrophs: use pre-formed organic matter

        • Not autotrophs, not photosynthetic

    • Fungi grow into, through their food

      • Release extracellular enzymes, break down polymers into LMW compounds for transport

    Fungi terminology and structure
    Fungi terminology and structure

    • Hypha (singular) hyphae (plural): thread

      • Hyphae may be partially separated into cells or not at all (ceonocytic).

        • Cytoplasm is continuous throughout hypha

    • Mycelium (plural mycelia): a mass of hyphae

      • Like a bacterial colony except really all one organism.

    • Some fungi are molds, some are yeasts

      • Yeasts are oval, unicellular

      • Dimorphic: able to grow as either form.

        • Typical of some disease-causing fungi

    Impacts of fungi
    Impacts of Fungi

    • Disease: mycosis (plural mycoses)

      • Superficial (on hairs, nails)

      • Cutaneous (dermatophytes, in skin (athlete’s foot)

      • Subcutaneous (deeper into skin)

      • Systemic (in deeper tissues, usually via lungs)

        • Opportunists: serious disease when immune system is depressed.

    • Antibiotic production

      • Penicillium, Cephalosporium

    • Decomposition; Food industry (soy sauce)

    Classification of fungi
    Classification of fungi

    • By sexual reproductive structures

    • Fungi reproduce both asexually and sexually

    • Deuteromycota = Fungi Imperfecti

      • No longer a valid classification

      • Contained fungi that couldn’t be coaxed into having sex

      • Through morphological and molecular means (e.g. DNA analysis), being distributed into the other 3 phyla of fungi.

    Classification 2

    • Zygomycota: produce zygospores

      • Example: Rhizopus

      • Fusion of hyphae (haploid) of opposite mating types produces zygospore (diploid).

      • Zygospore produces a zygosporangium with haploid spores that are released.

      • Asexually, sporangium containing spores.


    Zygospore images/332/Zygomycota/ fungi.unks.html

    Classification 3

    • Ascomycota: the sac fungi

    • Sexual spores produced inside an ascus (sac)

    • Asexual spores are called conidiospores or conidia (singular conidium)

    • Many types of common molds are ascomycetes.


    conidia nwfg/ascus.htm fungos%20e%20micoses.htm aspergillus_ear_rot.html

    Classification 31

    • Basidiomycota: the club fungi or mushrooms

    • After extensive growth of hyphae, opposite mating types fuse and above ground mushroom is formed.

    • Sexual spores are called basidiospores; asexual conidia can also be formed.

    Close-up of gills bn106.htm ../fungi/parasol.htm