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