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

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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
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