Bacteriology 304: The Beta-Galactosidase Page |
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Despite the "archived" nature of this site, this and other pages which contain background material may get updated from time to time. Included herein is a new (2007) summary of regulation associated with the lac operon. Also on this page is the same old (2003) set of very rough class data that can be used to graph beta-galactosidase activity vs. time (on linear paper) and absorbance vs. time (on semilog paper), comparing two strains and their growth with glucose vs. lactose. | |||
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A question from a Bacteriology 304 quiz given August, 2007: What should theoretically happen when a typical strain of Escherichia coli is inoculated into a medium containing high amounts of both glucose and lactose? The two-part answer:
A review of activation and repression of the Lac Operon:
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| strain & medium | time (min) | A420 | A600 | time of assay (min) |
U/ml | U/(ml X A600) |
| mutant strain in MM+glucose | 0 | 0.033 | 0.03 | 8.33 | 1.44E-05 | 4.80E-04 |
| 15 | 0.34 | 0.05 | 7.033 | 1.76E-05 | 3.52E-04 | |
| 30 | 0.34 | 0.04 | 6.67 | 1.86E-05 | 4.64E-04 | |
| 45 | 0.04 | 0.05 | 7.0 | 2.08E-05 | 4.16E-04 | |
| 60 | 0.066 | 0.06 | 7.0 | 3.43E-05 | 5.71E-04 | |
| 75 | 0.109 | 0.12 | 7.033 | 5.64E-05 | 4.70E-04 | |
| 90 | 0.24 | 0.28 | 5.33 | 1.64E-04 | 5.85E-04 | |
| 105 | 0.246 | 0.24 | 5.5 | 1.63E-04 | 6.78E-04 | |
| 120 | – | – | – | – | – | |
| mutant strain in MM+lactose | 0 | 0 | 0.009 | 10.0 | 0 | 0 |
| 15 | 0.035 | 0.246 | 10.0 | 1.27E-05 | 5.17E-05 | |
| 30 | 0.055 | 0.303 | 10.0 | 2.00E-05 | 6.60E-05 | |
| 45 | 0.198 | 0.376 | 8.5 | 8.47E-05 | 2.25E-04 | |
| 60 | 0.207 | 0.468 | 4.53 | 1.66E-04 | 3.55E-04 | |
| 75 | 0.247 | 0.562 | 4.33 | 2.07E-04 | 3.69E-04 | |
| 90 | 0.349 | 0.608 | 2.83 | 4.48E-04 | 7.38E-04 | |
| 105 | 0.85 | 0.756 | 1.69 | 1.83E-03 | 2.42E-03 | |
| 120 | – | – | – | – | – | |
| wild-type strain in MM+glucose | 0 | 0 | 0.03 | 5.0 | 3.64E-06 | 1.21E-04 |
| 15 | 0.015 | 0.078 | 5.0 | 1.09E-05 | 1.40E-04 | |
| 30 | 0.008 | 0.08 | 5.0 | 5.82E-06 | 7.27E-05 | |
| 45 | 0.02 | 0.17 | 5.0 | 1.45E-05 | 8.56E-05 | |
| 60 | 0.021 | 0.18 | 5.0 | 1.53E-05 | 8.48E-05 | |
| 75 | 0.024 | 0.26 | 5.0 | 1.75E-05 | 6.71E-05 | |
| 90 | 0.019 | 0.4 | 5.0 | 1.38E-05 | 3.45E-05 | |
| 105 | 0.016 | 0.49 | 5.0 | 1.16E-05 | 2.37E-05 | |
| 120 | – | – | – | – | – | |
| wild-type strain in MM+lactose | 0 | 0 | 0 | 10.0 | 0 | 0 |
| 15 | 0 | 0.07 | 10.0 | 0 | 0 | |
| 30 | 0.038 | 0.03 | 10.0 | 1.38E-05 | 4.61E-04 | |
| 45 | 0.024 | 0.04 | 10.0 | 8.73E-06 | 2.18E-04 | |
| 60 | 0.078 | 0.06 | 10.0 | 2.84E-05 | 4.73E-04 | |
| 75 | 0.21 | 0.07 | 10.0 | 7.64E-05 | 1.10E-03 | |
| 90 | 0.247 | 0.14 | 10.0 | 8.98E-05 | 6.42E-04 | |
| 105 | – | – | – | – | – | |
| 120 | – | – | – | – | – |
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Page last modified on 8/10/07 at 9:15 PM, CDT. |