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2010-10-31 03:18:07
Microbiology Test

10.1 Slide 12
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  1. Time Scale of Life on Earth
    • Earth formed ~4.6BYA
    • Oldest living fossils (stromalites) are 3.5BYA
    • Earliest life forms evolved in anoxinc environment ~3.8BYA
    • Probionts-precell without all final characteristics. composed of RNA surrounded by liposome
  2. Stanley Miller et al.
    • 1950's: Tried to make bldg blocks from proposed earth components (H2, H20, CH4, NH4)
    • Added heat & electrical discharge. Generated AA's
    • Other experiments using HCN. Different starting material made sugars, nt's, and lipids
  3. Spontaneous Developement of other Cellular Components
    • Clay or Fe2S surfaces catalyze formation and growth of lipids vesicles (which encapsulate RNA
    • Early fueling systems used FeS, H2S, H2
  4. RNA World model (Walli Gilbert)
    • Early life forms based on activities of RNA
    • RNA can direct nt synthesis, self replicate, catalyze polypeptide formation, serve regulatory function
    • DNA (more stable) took over genomic role
    • Proteins took over cellular functions
  5. Evolution of Eukaryotes
    • 1-Celled eukaryotes arose 1.5-2 BYA
    • Eukaryotic nucleus contain genes from bacteria and archae
    • Either endosymbiosis or nuclear fusion from archae w/bacteria
    • Endosymbiosis is favored model
    • Mitochodria evolved from Alpha-proteobacteria
    • Chloroplasts evolved from cyanobacteria related to prochlorococcus
  6. How Evolution Among Microbes is Studied
    • Gene sequence (most prevalent) of SSU rRNA or housekeeping genes. Reflects evolutionary relationships
    • Morphological analysis. in early stages and misleading
    • Physiological and metabolic characteristics. can be misleading
  7. Genomic Fingerprinting
    • Use of restriction enzymes and PCR to classify genomic characteristics w/out sequencing whole genomes
    • can be used for ribosomal genes (ribotyping)
    • housekeeping/non-ribosomal genees (RFLP, restriction fragment length polymorp
    • Intergenic highly repetitive genetic sequences used to classify humans or organisms (Short Tandem Repeats)
  8. Phylogenetic Trees
    • Demonstrate relationship of all the organisms together
    • Distance between 2 organisms related to the degree of homology
    • Probionts somewhere at root of tree
  9. Prokaryotic Diversity
    • May be as many as 10 million prokaryotic species
    • 8000 species characterized into 40 different phyla
    • Most species cannot be cultivated in lab (~1%)
    • Species may be comprised of many strands, and evolution quite rapid
    • Horizontal transmission of genetic material
  10. Taxonomy
    • Based on SSU gene sequence
    • Names of orders (end in ales), familes (end in aceae)
    • Biovars: Biological variance
    • Morphovars: members of same species, with different morphology
    • Serovars: subspecies classification based on antibody analysis
  11. Bergey's Manual of Analysis
    • 24 bacterial and 2 archae phyla
    • Gram (+) characterized based on their GC (nucleotide) contect