1' How does conjugation work

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Sex in Bacteria How do bacteria exchange DNA
1. How does conjugation work?
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Fig. 14.9
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Fig. 14.11
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Fig. 14.12a
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Fig. 14.12b
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Fig. 14.13
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Fig. 14.14
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Fig. 14.15
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Fig. 14.16
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Fig. 14.17
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What question did Tatum and Lederberg set out to
answer? What led them to expect bacteria
exchanged genetic information? Why did he pick
the bacteria (E. coli) he used as starting
material?
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Why did Lederberg want to use multiple mutations?
How did he get multiple mutations? What kind of
mutations are made by X-rays And what kind by UV
light?
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What did Lederberg do to get recombinants?
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Other possible explanations Cross feeding
(syntropism) Transformation
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After conjugation what are the most common
products? What do the rare classes
represent? Did recombination occur in both
directions?
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Did all possible parental combinations lead to
prototrophs? What must E. coli K12 have for
Lederbergs Experiments to have worked? Why is
frequency of prototrophs so low?
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Is this recombination mechanism equivalent to
sexual recombination in eukaryotes?
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Bacterial genomes differ in gene content even
within one species
Three E. coli genomes K12, UPEC 536 and UPEC
CFT073. Blue core genome Red 2 pathogens
only Green 536 only Orange in both pathogens
but in different locations
From Brzuszkiewicz et al 2006 PNAS 103, 12879.
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Whole genome comparisons of bacterial genomes
reveal differences in phage content and DNA
islands
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Plant pathogens differ in content and location
of virulence genes.
tomato
bean
Compare location of type III effectors In two
genomes of Pseudomonas syringae.
Horizontal transfer is source of Variation for
virulence factors
From Chang et al 2005 PNAS 102, 2549.
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Transduction Phage integrate Excise Re-infect
and transfer chromosomal DNA between strains
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Fig. 14.19
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Fig. 14.20
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Fig. 14.21
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Fig. 14.22
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DNA exchange in bacteria leads to development of
new niches, Adaptation to new hosts, Escape from
host defense mechanisms