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THE PROKARYOTES

THE PROKARYOTES. Systematics. Focus on animals and plants History limited to 20% of evolutionary time How to classify prokaryotes? Limited in morphological characters. Carl Richard Woese. 1928-2012, USA; Developed system based on 16S rRNA in 1977. Flow of information in a cell….

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THE PROKARYOTES

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  1. THE PROKARYOTES

  2. Systematics • Focus on animals and plants • History limited to 20% of evolutionary time • How to classify prokaryotes? Limited in morphological characters

  3. Carl Richard Woese 1928-2012, USA; Developed system based on 16S rRNA in 1977

  4. Flow of information in a cell…

  5. DNA molecule • When DNA is transcribed, the result is an RNA molecule Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Codon Translation Polypeptide Amino acid Figure 10.10

  6. DNA molecule • When DNA is transcribed, the result is an RNA molecule • RNA is then translated into a sequence of amino acids Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Codon Translation Polypeptide Amino acid Figure 10.10

  7. Ribosomal Function A typical prokaryotic cell may have 10,000+ ribosomes

  8. Where does rRNA enter the picture?

  9. Ribosomal Structure Two subunits

  10. Ribosomal subunits=rRNA molecules + proteins

  11. Prokaryotes Eukaryotes

  12. What’s the ‘S’? • Svedberg units: a measure of how quickly particles sediment in an ultracentrifuge

  13. What’s the ‘S’? • Svedberg units: a measure of how quickly particles sediment in an ultracentrifuge • Larger the particle, the greater its S value • Smaller subunit of a ribosome sinks slower than the larger subunit

  14. Why then does 5S + 23S = 50S?

  15. Why then does 5S + 23S = 50S?Shape AND size determine sedimentation rate…

  16. Ribosomal RNA Molecules • Components of the ribosomes of ALL ORGANISMS • Changes in nucleotide sequence indicative of evolutionary history • “highly conserved molecules”… What does this mean?

  17. Ribosomal Function • PROTEIN SYNTHESIS • Not much room for error! • Disruption of ribosome structure likely to disrupt protein synthesis… Life threatening!

  18. Practical applications… • Some antibiotics (e.g. erythromycin and streptomycin) work by targeting the 70S ribosomes • Alter shape and prevent bacteria from synthesizing proteins needed to survive • Why are our own ribosomes not affected by the same drugs???

  19. A modification of Woese from Brock et al. (1994).

  20. Composite tree from Daubin et al. (2002)

  21. Gram Stain and Structure

  22. Eubacteria • >9 Kingdoms • Same type of ribosomes • Polysaccharide of outer wall made of Murein • Most groups involved in global nutrient cycling • Many of economic importance • Disease • Other functions (e.g. antibiotic producers)

  23. Proteobacteria • Disparate functional groups joined by molecular sequences • Likely the source of mitochondria

  24. Alphaproteobacteria • Rikettsias (typhus Rocky Mtn spotted fever • Rhizobias (N-fixing bacteria) • Likely the ancestor of mitochondria was from this group

  25. Gammaproteobacteria • Usually small rods or cocci • Causative agents of Bubonic Plague, Tuleremia, Legioner’s Disease, Cholera • Includes Escherichia coli

  26. Spirochaetobacteria • Spiraled with internal flagella • Many are free-living • Causative agents of Lyme disease, syphilis, yaws, and relapsing fever

  27. Cyanobacteria • Like free-living chloroplast • Group from which chloroplasts appeared • Form filaments, colonies • Very large for bacteria • Some produce toxins • Many are nuisance algae in over-fertilized waters • Source of most atmospheric oxygen, especially prior to eukaryotes

  28. Firmicutae • Lack second outer membrane of Eubacteria • Gram positive

  29. Aphragmabacteria • Tiny, smallest genome of any non-virus • No walls • Obligate parasites • One causes pneumonia; many plant pathogens

  30. Anoxyphotobacteria • Obligate anaerobes • Causative agents of botulism and tetanus • Botox • Common in soil and animal digestive systems

  31. Endosporobacteria • Produce resistant spores • Many major human pathogens, including anthrax, staph (including methicillin-resistant Staphylococcus aureus), strep • Includes Lactobacillus

  32. Actinobacteria • Many are slow-growing and fungus-like • Antibiotic sources (e.g. streptomycin, actinomycin) • Causative agents of leprosy and tuberculosis; diptheria • Bacteria which cause holes in Swiss cheese • Bifida, a necessary commensal in our lower bowel

  33. Deinococcobacteria • Thermophiles • Deinococcus withstands 6,000 rads (and up to 1500 megarads) • Thermus, found at Yellowstone, enzymes used for PCR

  34. Archaea • Differ from the Eubacteria • Form of ribosomes • No murein • Different lipids • Different RNA polymerase

  35. Crenarchaea • These are the hyperthermophiles • They tend to inhabit very hot environments that are rich in sulfur

  36. Euryarchaeota • Halobacteria • Methanobacteria • Thermoplasmobacteria

  37. Viruses • Non-cellular • Usually nucleic acid and protein • Types • DNA (ss & ds) • RNA (ss & ds) • DNA RT • RNA RT • Prions

  38. Some Human Viral Diseases • Herpes • Smallpox • Hepatitis (B, C, D) • Yellow Fever • Dengue fever • West Nile • HIV • Ebola • Rabies • Chicken Pox /Shingles • Rubella (German Measles) • Influenza • Polio • Mumps • Measles • Epstein-Barr • Hemorrhagic fever • Rota • Rhinovirus • Transmissible spongiform encephalopathy (TSE)

  39. Theories on Origin of Viruses • Regressive Hypothesis • Cellular Origin Hypothesis • Coevolution Hypothesis

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