Sex in Bacteria How do bacteria exchange DNA 1 How does conjugation work Fig 14 9 Fig 14 11 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 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 What did Lederberg do to get recombinants How did Lederberg rule out possible explanations for his data that did not involve exchange of genetic information between strains eg Cross feeding syntropism Transformation After conjugation what are the most common products What do the rare classes represent Did recombination occur in both directions Fig 14 11 Tatum and Lederberg 1947 Davis U tube experiment 1950 Fig 14 12a Fig 14 12b Fig 14 13 Fig 14 14 Fig 14 15 Fig 14 16 Fig 14 17 Is this recombination mechanism equivalent to sexual recombination in eukaryotes 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 Whole genome comparisons of bacterial genomes reveal differences in phage content and DNA islands 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 DNA exchange in bacteria leads to development of new niches Adaptation to new hosts Escape from host defense mechanisms
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