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  1. 1. Host Defense Dicer Animals Fig. 8.16 dsRNA – immune system Dicer cleaves dsRNA into shorter segments – RNA interference siRNA (RNAi) RISC • Dicer – dsRNA RISC complex binds siRNA and nuclease separates the strands • siRNA – short RISC complex finds interfering RNA mRNA complementary to siRNA • RISC – RNA- mRNA induced silencing complex RISC cleaves mRNA • Slicer – ssRNA nuclease RNA fragments degraded by Slicer
  2. 2. Fig. 20-7a in the 11th edition
  3. 3. Chemical antimicrobial agents used to control microorganisms that are harmful to humans: Sterilants destroy all forms of microbial life ; Disinfectants kill microorganisms, but endospores are typically resistant Sanitizers reduce the microbial load but may not eliminate all microorganisms Antiseptics kill or inhibit growth of & Germicides microorganisms on living tissue
  4. 4. 1888-1955 Alexander Fleming 1929 discovered antimicrobial effects of penicillin G made by the fungus Penicillium on Staphylococcus by chance 1945 Nobel Prize in Medicine - Fleming, Howard Walter Florey and Ernst Boris Chain
  5. 5. Vancomycin • Glycopeptide antibiotic • Binds to pentapeptide of the peptidoglycan precursor • Produced by a soil microbe Amycolatopsis orientalis • Effective against Gram- positive Bacteria
  6. 6. Platensimycin • Produced by Streptomyces platensis • Inhibits fatty acid biosynthesis enzyme Fig. 27.25
  7. 7. An example of an echinocandin
  8. 8. An example of a polyoxin
  9. 9. Bacterial cell with chromosomal mutation Bacterial cell not altering target of antibiotic resistant to antibiotic resistant to antibiotic Transformation Transfer of free DNA Lysis of cell Previously susceptible cell is now resistant to antibiotic
  10. 10. Bacterial cell with R plasmid Bacterial cell not resistant to antibiotic resistant to antibiotic Chromosomal DNA Conjugation Copy and Transfer of R plasmid Previously susceptible cell is now resistant to antibiotic
  11. 11. Fig. 27.29 Candida albicans * Key: Acinetobacter sp. Gram-negative Enterococcus faecium* Gram-positive Streptococcus pneumoniae Gram-positive/ acid-fast Mycobacterium tuberculosis* Fungus Haemophilus ducreyi Salmonella typhi Antimicrobial Haemophilus influenzae drug resistance Neisseria gonorrhoeae human pathogens Pseudomonas aeruginosa* continue to Salmonella sp. emerge. Shigella dysenteriae Shigella sp. Other gram-negative rods Staphylococcus aureus* 1950 1960 1970 1980 1990 2000 2010 Year
  12. 12. Eon Billion Evolutionary Oxygen Metabolic and Fig. 14.7 years ago event level other highlights Comparable to 0 Extinction of the dinosaurs Fig. 11.8 in the Phanaerozoic Cambrian 11th edition 0.5 Early animals Multicellular 20% 1.0 eukaryotes Precambrian 10% Proterozoic 1.5 First eukaryotes 1% Ozone shield 2.0 Great oxidation 0.1% 2.5 event Cyanobacteria Oxygenic photosynthesis 3.0 (2H2O O2 + 4H) Archaean Purple and green Anoxygenic photosynthesis 3.5 bacteria (H2S S0 + 2H) Anoxic First cellular Methanogenesis 4.0 life (CO2 + 4H2 CH4 + 2H2O) Hadean Formation of crust and ocean 4.5 Formation of Earth
  13. 13. Fig. 11-9 in the 11th edition (oxygenic) (aerobic)
  14. 14. The Hydrogen Hypothesis – how the first eukaryotic was formed? Host cell - Archaea Symbiont cell - dependent on Bacteria H2 for electron producing H2; source to make lipid gene transfer; energy precursor of Symbiont cell – mitochondrion photosynthetic cyanobacterial- like ancestor
  15. 15. Fig. 14.15 Fig. 14.14 Fan-shaped Dichotomous outgroup
  16. 16. Branches show order of descent and node ancestry. Branch length reprepresents number of nucleotide changes Fig. 14.14d Internal nodes denote common ancestor Nodes at the tips denote species/strains
  17. 17. Fig. 11.20 in 11th edition
  18. 18. Fig. 11.21 in 11th edition