Bacterial Conjuation Questions

1. Was the initial E. coli/R factor recipient culture sensitive or resistant to ampicillin? Why? Sensitive; because it wasn’t able to grow on the MAC + AMP plate. It has the ability to uptake the R-factor plasmid by conjugation which would give it the resistance characteristic against AMP, but until it does this, E. coli will be sensitive. 2. Was the initial S. typhimurium/R factor donor culture sensitive or resistant to ampicillin? Why? Resistant; it has the R-factor plasmid already present and so it can therefore grow on the MAC + AMP plate. In our results this fact proves to be right. 3. After conjugation was E. coli/R factor recipient culture sensitive or resistant to ampicillin? Why? Resistant; S. typhimurium and transfer a copy of the R-factor plasmid to E. coli and therefore E. coli was able to grow on the MAC + AMP plate. 4. Why did the two cultures need to be incubated together? Incubation allows the two organisms to come into contact and combine; the heat simulates the temp. that each grow more readily in. 5. Which organism is lactose positive? How do you know this? E. coli ferments lactose and therefore turned the MAC plates pinkish and had these colored colonies. 6. Which organism is lactose negative? How do you know this? S. typhimurium doesn’t ferment lactase and therefore turned the plates yellowish and had tan colonies grown on the plates. 7. Were you able to obtain pure cultures of ampicillin resistant E. coli and S. typhimurium bacteria?Yes; tan and pinkish colonies were observed.