Explore BrainMass

# Transformation and competent cells

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

1. If you spread 0.1 ml of 10-3 of a sewage sample on a plate, and obtained 221 colonies on the plate after incubation, how many CFU/ml were present in the undiluted sewage sample? Please show work

2. How can you make E.coli cells competent so that they can be transformed?

3. What is the appearance of transformed bacterial colonies?

4. After transformation procedure, your test tube may contain both transformed and nontransformed cells.
a. which will grow on LB plate? Which will grow on LB/amp plates?
(+ DNA or - DNA)

5 Why is there heavy growth on LB and very little growth on LB/amp?

5. What is the reason to plate E.coli cells on LB/amp?

6. Why are there both green and white colonies on LB/amp?

https://brainmass.com/biology/prokaryotic-cells/transformation-competent-cells-120762

#### Solution Preview

1.If you spread 0.1 ml of 10^-3 of a sewage sample on a plate, and obtained 221 colonies on the plate after incubation, how many CFU/ml were present in the undiluted sewage sample? Please show work

0.1ml of 10-3 dilution: 221 colonies.

1ml would contain: 221 x 10 = 2210 colonies.

10^-3 dilution has 2210 CFU/ml.

Therefore, 100 dilution, that is the original sewage sample will have: 2210 x 1000 CFU/ml or 2.21 x 10^6 CFU/ml.

Therefore, in the undiluted sewage sample, the count was 2.21 x 10^6 CFU/ml.

2.How can you make E.coli cells competent so that they can be transformed?

E.coli cells can be made competent by calcium chloride treatment. The bacterial cells are given "shock", which involves cooling the bacteria in ...

#### Solution Summary

E.coli cells can be made competent by calcium chloride treatment. The appearance of transformed bacterial colonies are determined.

\$2.19