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 multiplemutations?
How did he get multiple mutations?
What kind of mutations are made by X-rays And what kind by UV light?
How did Lederberg rule outpossible explanations for hisdata that did not involve exchange ofgenetic 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?
Three E. coli genomes:K12, UPEC 536 and UPEC CFT073.Blue: core genomeRed: 2 pathogens onlyGreen: 536 onlyOrange: in both pathogens but in different locations
From Brzuszkiewicz et al 2006 PNAS 103, 12879.
Bacterial genomes differin gene content even withinone species
Plant pathogens differ in content and location of virulence genes.
Horizontal transfer is source of Variation for virulence factors
Compare location of type III effectorsIn two genomes of Pseudomonas syringae.
tomato
bean
From Chang et al 2005 PNAS 102, 2549.