IGEM:IMPERIAL/2006/ProjectCalendar/2006-8-21

Monitoring Cell Populations

After meeting with Dr. David Leak, the idea of using 3 different antibiotics to monitor cell populations was found promising by the group
By adding tetracycline and kanamycin antibiotic resistance genes to the different cell populations respectively, cell populations cal be monitored by taking samples and plating them on the respective antibiotic plate
This needs an extra ligation step (3 days) !!
Decided to prepare all the plasmids and DNA ready to insert the antibiotic resistance gene if we still have time and need to do it
There is an alternative check that we should do regardless beforehand to get some idea of the growth rates of the two populations:
- Grow up the two cell cultures separately and at different times in the grwoth phase measure the OD
- If the OD is similar, this will suggest same growth rates and the cell populations will be more probable to stay at a ratio of 1:1
- If the OD differs very much, we should monitor cell populations throughout using the antibiotic resistances

Deepti -Talking to Dr. Jensen this morning, it seems that the 3 antibiotic method is not very accurate an requires extra ligations steps which can be avoided.
- Waiting for plated samples to grow will require atleast a day before we can assess the differences in population sizes.
- The number of bacteria in the plated samples does not necessarily accurately reflect the relative proportion in the common broth culture.
- Even if the plating method were to be an accurate measure of the colony sizes in the broth culture, we could still only record, and not control population sizes
According to Dr. Jensen, the best way to do it would be the OD method.
- By growing up the bacteria separately, we can measure their separate growth rates which, hopefully, should not be too disimilar.
- When mixing the two cultures, the ODs should be equal, and preferably, between 0.6 and 0.8. -Deepti