D2O adaptation, Microorganisms, Water Type Effects on Organism Growth, Yeast

Basic Observations of the D2O Adapted Yeast compared to WT Yeast

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After having been adapting wild type yeast to D2O for the past 49 days, I’ve been making some basic observations regarding their growth. Initially wild type (wt) yeast exhibits slowed growth in D2O. Usually the first 24 hours there is relatively little growth and they yeast takes about 72 hours to reach the maximum growth (cell number) as yeast grown in DI water or DDW. But there are also some differences between adapted yeast and wt yeast. I’ve yet to quantify most of these but I’ve noticed some things:

Yeast grown in liquid YPD media. On the left is D2O adapted yeast grown in D2O YPD. On the right is wild type yeast grown in DDW. Yeast was grown at 30C and shaken (not stirred) for 24 hours.

The first of which is the aggregation of the cells in the mediums. D2O adapted yeast (grown in D2O) seem to be less prone to aggregation/clumping. In the image above, there is a pretty high cell count (observed by the cloudy appearance of the medium) in the test tube on the left. There is some settling of cells (which would indicated the cells are clumping), but compared to the test tube on the right (wt yeast grown in DDW) that’s really not a problem. It is important to note that when both samples are resuspended their absorbance are almost identical (3.256 for D2O yeast vs 3.249 for DDW yeast).

We’ve also noticed a difference in color between the cells. It’s not yet sure whether the cells are in face a different color or if this is related to the aggregation characteristic.

Obviously tests will need to be done, and I’m going to get on it. Most of which will be microscope analysis, but hopefully I can speak with some friends over at Cancer Research to perform some advanced tests on the cells.

I’ve also been trying to determine if my yeast cells are officially D2O adapted, and my latest experiment may finally put my own skepticism to rest.

Yeast grown on YPD agar made with 99.9% D2O. On the left is wild type yeast, and on the right is yeast adapted to D2O. The yeast was incubated for 24 hours at 30C.

After 24 hours of incubation, wt yeast grown in D2O greatly struggles (left sample) while my potentially adapted yeast grows like crazy. That looks super conclusive, especially because the same culture of wt yeast grows really well on normal YPD agar plates:

Yeast grown on YPD agar plates (commercial, made with DI water). On the left is wild type yeast and on the right is D2O adapted yeast. The yeast was incubated at 30C for 24 hours.

But interestingly enough, the D2O adapted yeast appears to grow on H2O media much better than wt yeast. If anything I would have assumed the same growth, but the results above are ridiculous. Tempering excitement for a minute, more tests will need to be done, and tomorrow I’ll have some (hopefully) more conclusive data.

With that said, I can’t help but be excited for the future of the project. Let’s see what tomorrow brings!