1. Chapter 8 The Genetics of Bacteria and Their Viruses
Multi-Drug-Resistant Bacteria (MDRB)
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2. Chapter Outline Viruses and Bacteria in Genetics
The Genetics of Viruses and Bacteria
Mechanisms of Genetic Exchange in Bacteria
The Evolutionary Significance of Genetic Exchange in Bacteria
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3. Bacteria and Viruses in Genetics
Small size (~2 um)
Rapid reproduction (~ hrs)
Selective media (e.g., antibiotics)
Relative Simple structures and physiology
Complete genome sequences
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4. The Genetics of Viruses
Viruses (DNA-RNA) can only reproduce by infecting living host cells.
Bacteriophages are viruses that infect bacteria.
Several important genetic concepts have been discovered through studies of bacteriophages.
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5. Bacteriophage T4 Double-stranded linear DNA genome Protein head
Genome contains 168,800 base pairs and 150
characterized genes
Lytic phage
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6. T4 DNAse: (Specific) Lysosyme: 5-hydroxymethylcytosine (HMC) Cell wall
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7. Bacteriophage Double-stranded linear DNA genome
Genome contains, 48,502 base pairs and about 50 genes
May be lytic or lysogenic (inserted in the bacterial chromosome)
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8. Differential genes expression
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9. Recombination process: ---site-specific
attP (virus) and attB (bacteria)
--- int gene (integrase)
--- GCTTTTTTATACTAA
--- CGAAAAAATATGATT
--homologous recombination
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10. The Genetics of Bacteria
Bacteria contain genes that mutate to produce altered phenotypes.
Gene transfer in bacteria is unidirectional—
from donor cells to recipient cells. S r
Energy (Lac / lac); Synthesis Trp / trp; Resistant Amp / Tet
Monopliod to monoploid?
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11. Bacteria One main chromosome with a few thousand genes.
Variable number of plasmids and episomes.
Asexual reproduction by simple fission.
(Para) sexual transformation of DNA.
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12. Phenotypes in Bacteria
Colony =one bacteria.
Colony color and morphology.
Nutritional mutants for energy sources.
(any sugars-galactose-Lac+ and Lac-)
Prototrophs-produce any metabolites- and auxotrophs- do note produce specific metabolites.
Antibiotic resistance (Ampr, Tetr, Purr).
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13. Bacterial colonies: Serratia marcencens P. aeruginosa.
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14. Recombination in Bacteria
--Small fragment to larger fragment (chromosome)
--Monoploid (to partial diploid)
-Donor to recipient cell
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15. Mechanisms of Genetic Exchange in Bacteria
Bacteria exchange genetic material through three different (para)sexual processes.
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16. Bacteria exchange genetic material through three different (para)sexual processes.
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17. The U-tube Experiment Transformation Conjugation Transduction
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18. TRANSFORMATION Streptococcus pneumoniae---Phenotypes
Polysaccharide capsule (S, type I,II, III, IV, V)
Type II, agglutination
Non- Polysaccharide capsule (R)
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19. Transformation Type IIIS to type IIR Transfer DNA Hydrophilic
Non-membrane permeable
Transporter
(competence-Com-protein)
Competent bacteria
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20. Transformation in Bacillus subtilis
A heteroduplex is a double-stranded (duplex) molecule of DNA originated by recombination of
single complementary strands derived from exogenous sources.

21. Conjugation in E. coli F+
DNA is transferred from a donor to acceptor cell,
F: Fertility factor ; F pili
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22. The F Factor in E. coli F+ factor: --Autonomous and integrated states
F’ factor: --Similar to F+ but with bacterial genes
F: Fertility factor
Hfr: high frequency recombination

23. Formation of Hfr Cells seq A -seq B seq A -seq B
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24. Conjugation
MODEL Replication: Rolling-cycle
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25. F- Hfr strs strr gal+ gal- lac+ lac- leu+ leu- thr+ thr- azis azir
tons
strr
gal-
lac-
leu-
thr-
azir
tonr 25

26. Selected medium:
-Thr, -Leu,
+Streptomycin (str)

27. Interrupted Mating Experiments
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28. Plasmids
A plasmid is a genetic element that can replicate independently of the main chromosome in an extrachromosomal state.
Most plasmids are not required for the survival of the host cell.
Plasmids in E. coli
F Factor (Fertility Factor)
R Plasmids (Resistance Plasmids)
Col Plasmids (synthesize compounds that kill sensitive cells)
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29. Episomes
An episome is a genetic element that is not essential to the host and that can either replicate autonomously or be integrated into the bacterial chromosome.
Integration depends on the presence of IS elements.
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30. © John Wiley & Sons, Inc.

31. Formation of an F’ Factor
Homologous DNA recombination, but some bacterial DNA is translocated to the plasmid.
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32. Transduction
In transduction, a bacteriophage transfers DNA from a donor cell to a recipient cell.
In generalized transduction, a random fragment of bacterial DNA is packaged in the phage head in place of the phage DNA (normal Excision).
In specialized transduction, recombination between the phage chromosome and the host chromosome produces a phage chromosome containing a piece of bacterial DNA (abnormal Excision).
Auxotrophic Salmonella typhimurium:
tyr, phe, trp and met, his.
Infected with P22 bacteriophage
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33. Normal Excision of  Prophage
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34. Anomalous Excision of  Prophage
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35. Specialized Transduction
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36. Three parasexual processes—transformation, conjugation, and transduction—occur in bacteria.
These processes can be distinguished by two criteria: whether the gene transfer is inhibited by deoxyribonuclease (DNAase) and whether it requires cell contact.
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37. The Evolutionary Significance of Genetic Exchange in Bacteria
Genetic exchange is as important in bacteria as it is in other organisms.
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38. Genetic Exchange in Bacteria
Mutation is the source of new genetic variation.
(UV radiation)
Recombination produces new combinations of allele.
(normal and abnormal recombination)
Transformation, conjugation, and transduction generate new combinations of genes in bacteria to allow bacteria to adapt to new environments.
(soil, sewers and polluted waters) (animal/plants)
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39. Bacteria genetically engineer plants with the Ti plasmid to control their differentiation (tumorigenic- Crown gall disease).