DDW and 30% D2O starter culture analysis

Data on figshare:

24 hour growth of e. coli in DDW and D2O. Anthony Salvagno. Figshare.
Retrieved 22:57, Apr 26, 2012 (GMT)



  • So I mentioned several times that these cultures aren’t optimal, which is why I resetup the experiment today. But I did get some interesting results.
  • The absorption readings on the nanodrop were:
    • 30% D2O – 0.782
    • 99% DDW – 1.239
  • So the growth over 24 hours in 30% D2O was ~63% less.
  • Interestingly the number in 30% D2O is similar to yesterday’s time sampling data, both in number and consistency. The D2O sample reached 0.7 the fastest, but started to decline at that point, whereas the other samples continue to increase.
  • My data collection technique may be a bit weird to those looking at the raw data.
    • I analyzed samples of lb-water (where water is the water type of the lb media) to see how much difference in the absorption spectrum there were between the water types. There wasn’t much difference except from the DI sample, which had a much larger absorption reading than the other 4 readings.
    • I also blanked the nanodrop of each water type before measuring that water type. Example: I would insert the LB-DDW and blank it, and then measure the culture labeled DDW. Same went for the 30% D2O sample.
    • I did one measurement of the DDW sample after blanking in LB-DI to compare to the LB-DDW blank reading. The comparison is off by about as much as the absorbance of the LB-DDW and LB-DI which is a 0.017 difference.
  • All that leads me to think that for some reason growth in D2O isn’t slower, but has a peak meaning for some reason the media can only sustain so much culture after a while. Tomorrow I’ll try for a longer time series study to see if the decline is real or if that was some weird glitch that happened.