Major groups of Prokaryotes (26)

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Major groups of Prokaryotes (26)
2012-02-13 13:24:26

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  1. Spirochetes

    •Gram-negative, motile, chemoheterotrophic; they have unique axial filaments (modified flagella) that rotate.

    •Many are human parasites, some are pathogens (syphilis, Lyme disease), others are free living.
  2. Chlamydias

    •Extremely small, gram-negative cocci, live only as parasites within cells of other organisms. Can take up ATP from host cell with translocase.

    •Complex life cycle w/ two forms- elementary bodies and reticulate bodies.

    •Some are pathogens causing sexually transmitted diseases, some pneumonia.
  3. High-GC Gram-positives (actinobacteria)

    •High G-C/A-T ratio in DNA

    •Form elaborately branching filaments, some reproduce by forming chains of spores at tips.

    •Most antibiotics are from this group, also includes Mycobacterium tuberculosis.
  4. Cyanobacteria

    •Photoautotrophs use chlorophylla; produce O2

    •Often associated with polluted conditions.

    •Some can fix nitrogen via specialized cells known as heterocysts.

    Eukaryote chloroplasts are derived from endosymbiotic cyanobacteria
  5. Low-GC Gram-positives (firmicutes)
    • Bacteria
    • •Low G-C/A-T. mostly gram-positive (includes Staphylococcus, and organisms responsible for anthrax and botulism), but some are gram-negative; some have no cell wall

    •Some produce endospores—heat-resistant resting structures; can survive harsh conditions because it is dormant.

    •Endospore becomes active and divides when conditions improve.

    •Mycoplasmas have no cell wall, are extremely small, and have very small genome. May be the minimum amount of DNA needed for a living cell.
  6. endospores
    • (firmicutes)
    • heat-resistant resting structures;
    • can survive harsh conditions because it is dormant.
  7. Mycoplasmas
    • (firmicutes)
    • have no cell wall, are extremely small, and have very small genome. May be the minimum amount of DNA needed for a living cell.
  8. Proteobacteria (purple bacteria)
    •Largest group of bacteria—high diversity of metabolic phenotypes.

    •Common ancestor was photoautotrophic; as they encountered new environments, the delta and epsilon groups lost ability to photosynthesize. In other 3 groups, some evolutionary lineages became chemolthotrophs or chemoheterotrophs.

    •Includes some nitrogen-fixing genera such as Rhizobium; E. coli is also proteobacterium.

    •Proteobacteria that are human pathogens: Yersinia pestis (plague), Vibrio cholerae (cholera), and Salmonella typhimurium (gastrointestinal disease).
  9. Archaea
    •The separation of Archaea was originally based on rRNA gene sequencing; supported by sequencing an entire genome—more than half the genes were unlike any in the other two domains.

    •Archaea are famous for living in extreme environments: high salinity, high temperatures, high or low pH, and low oxygen. But many others live in habitats that are not extreme (e.g. soils).
  10. Archaea are divided into two main groups,___________ and__________, plus 2 recently discovered groups
    Euryarcheota, Crenarcheota
  11. _______ are known only by evidence from DNA isolated from hot springs.
  12. ________ are named due to their small size. Discovered in deep sea vents off Iceland; they live attached to cells of the crenarcheota Ignicoccus.
  13. •Two characteristics shared by ALL Archaea:
    1. no peptidoglycan in cell wall

    2. Distinct lipid composition of cell membrane
  14. Most bacterial and eukaryotic membrane lipids unbranched
    long-chain fatty acids connected to glycerol by __________.

    Unique Archaea lipids contain long-chain
    hydrocarbons that are branched, and connected to glycerol by __________.
    ester linkages.

    ether linkages (are a synapomorphy for archaea)
  15. lipid bilayers and lipid monolayers are both found in the______.
  16. Crenarcheota
    • Archaea
    • are both thermophilic and acidophilic (acid-loving).
  17. Euryarcheota
    • Some are methanogens; they produce methane (CH4) by
    • reducing CO2 (obligate anaerobes).

    Methanogens release 2 billion tons of methane per year. Many live in the guts of grazing mammals.

    Increased cattle farming and rice growing contributes methane to the atmosphere.
  18. •Extreme halophiles
    (salt lovers) have pink carotenoid pigments, easy to see. They have been found at pH up to 11.5. They live in the most salty, most alkaline environments on Earth.
  19. Thermoplasma
    is thermophilic and acidophilic, has no cell wall, aerobic metabolism, and lives in coal deposits; it has the smallest genome of the Archaea and its genome size is comparable to mycoplasmas.
  20. Consequences of infection depend on:
    Invasiveness of the pathogen—its ability to multiply in the host.

    Toxigenicity of the pathogen—its ability to produce toxins.
  21. Corynebacterium diphtheriae
    (diptheria) has low invasiveness, but the toxins it produces affect the entire body.
  22. Bacillus anthracis
    (anthrax) has low toxigenicity, but very high invasiveness—colonizes the entire bloodstream.
  23. Endotoxins
    (type of bacteria toxin)are released when certain gram-negative bacteria grow or lyse, are lipopolysaccharides forming part of outer bacterial membrane.
  24. Exotoxins
    (type of bacteria toxin) are soluble proteins released by living bacteria. Are highly toxic and often fatal.