Horizontal Gene Transfer Homework (10 pts)

1. Say you had gotten these results in the first week of Exercise 9:

	Plain LB	LB+ str	LB+amp	LB+str+amp
Strain I (strR)	G	NG	G	NG
Strain II (ampR)	G	G	NG	NG

What would be a possible explanation for this?

2. To perform a conjugation with our Escherichia coli strains, both strains are mixed together on a plate and then a single colony is streaked out onto new LB antibiotic plates. If you did not know whether the ampR gene or the strR gene was the one on the plasmid being transferred through conjugation, would you be able to tell just from these experimental results? Why or why not?

Plain LB	LB+ str	LB+amp	LB+str+amp
G	G	G	G

3. You performed a conjugation with both strains, then streaked the new colonies that grew from this mating onto fresh LB plates. Your results looked like this:

Plain LB	LB+ str	LB+amp	LB+str+amp
G	G	G	NG

Was your conjugation successful? Why or why not?

4. If we inoculated Strain I (strR) on Mueller-Hinton agar, and dropped a streptomycin disk on it, and incubated it overnight, would you expect to see a small zone of inhibition the next day, or a large zone of inhibition?

5. Why were the Legionella cells that had sterile water added unable to either grow or grow outside of the original inoculation site on our CYE plate?

6. The gene for GFP originally came from Aequorea victoria (jellyfish), not Legionella pneumophila.  Can you think of how the capability to transfer genes from other organisms into bacteria could be of benefit to humans?

7. Discuss ways in which conjugation differs from transformation (in our experiment).