figures not in textbook for exam 3
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Host Defense
Animals – immune system– RNA interference
(RNAi)• Dicer – dsRNA
nuclease
• siRNA – short interfering RNA
• RISC – RNA-induced silencing complex
• Slicer – ssRNA nuclease
Dicer
siRNA
mRNA
RISC
dsRNA
Dicer cleaves dsRNAinto shorter segments
RNA fragments degraded by Slicer
RISC cleaves mRNA
RISC complex findsmRNA complementary
to siRNA
RISC complexbinds siRNA and
separates thestrands
Fig. 8.16
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Fig. 20-7a in the 11th edition
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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 & Germicides
kill or inhibit growth of microorganisms on living tissue
;
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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
1888-1955 Alexander Fleming
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Vancomycin
• Glycopeptide antibiotic
• Binds to pentapeptide of the peptidoglycan precursor
• Produced by a soil microbe Amycolatopsis orientalis
• Effective against Gram-positive Bacteria
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Platensimycin
• Produced by Streptomyces platensis
• Inhibits fatty acid biosynthesis enzyme
Fig. 27.25
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An example of an echinocandin
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An example of a polyoxin
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Bacterial cell with chromosomal mutation
altering target of antibioticBacterial cell not
resistant to antibiotic
Transfer of free DNA
Previously susceptible cell is now resistant to antibiotic
Transformation
Lysis of cell
resistant to antibiotic
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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
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Key:
Gram-negative
Gram-positive
Gram-positive/acid-fastFungus
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
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Fig. 14.7Comparable to Fig. 11.8 in the 11th edition
Billionyears ago
Extinction of the dinosaurs
Phanaerozoic
Eon Evolutionaryevent
Oxygenlevel
Metabolic andother highlights
Proterozoic
Archaean
Hadean
Cambrian
Precambrian
20%
10%
Early animals
Multicellulareukaryotes
First eukaryotes
Great oxidationevent
Cyanobacteria
Purple and greenbacteria
1%
0.1%
Ozone shield
(2H2O
Oxygenic photosynthesis
O2 + 4H)
Anoxic (H2S
Anoxygenic photosynthesis
S0 + 2H)
(CO2 + 4H2
Methanogenesis CH4 + 2H2O)
First cellularlifeFormation ofcrust and ocean
Formation of Earth
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
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Fig. 11-9 in the 11th edition
(aerobic)
(oxygenic)
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The Hydrogen Hypothesis – how the first eukaryotic was formed?
Symbiont cell - Bacteria producing H2; lipid gene transfer; precursor of mitochondrion
Host cell - Archaea dependent on H2 for electron source to make energy
Symbiont cell – photosynthetic cyanobacterial-like ancestor
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outgroup
Fig. 14.14
Fig. 14.15
Fan-shaped
Dichotomous
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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
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Fig. 11.20 in 11th edition
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Fig. 11.21 in 11th edition