The effect of deuterium on the growth of yeast

by Oscar Richards, Journal of Bacteriology. Here is the link.

Before we get to the notes, I have to say I have no idea what journal this paper comes from. I have no details about it other than the fact that this paper comes from some lab at Yale and was received in 1934. Hmmm… anyways, some notes:

  • They use water with a specific gravity of 1.000061. After looking it up, specific gravity is the ratio of densities of one substance to a reference substance. In our case it’s probably D2O to H2O. Water should have a SG of 1 at same temp and pressure. The SG of pure D2O is something like 1.107. After thinking about this a lot, there is almost nothing you can infer from that number. They do however provide the ppm (part per million) which is 500 (they say 1 in 2000). Compared to SMOW, that is roughly 3.2 times more D. If I had to guess, I’d say they didn’t discover anything! But luckily I don’t have to guess. They wrote a paper about it.
  • Some other interesting numbers I thought about while comparing their SG to SMOW:
    • 500ppm is 0.05% D
    • 99.9% D2O (which is what I normally use) is 999,000ppm
    • For refresher, my DDW is <1ppm D and SMOW is 155.76ppm D
    • I inquired with Sigma-Aldrich about the ppm of their D2O, because 99.9% is not terribly descriptive when compared to the other isotope counts.
  • This paper is maddeningly frustrating! The data in table one is yeast grown in heavy water compared to yeast grown in DI water, but they don’t provide the reference details. They just give everything as a percentage compared to DI water. WHHHHYYY?!?!?!
  • They state “…Nor were significant differences found in the …mean cell size of the two populations of yeast grown under these conditions.”
  • Table 1 is full of the most uselessly descriptive information. They chart age, volume and weight of cells and the whole time I’m thinking it’s individual cells but turns out it’s a count of all the cells at once.
    • They use this device: photoelectric nephelometer to measure cell counts
  • Interesting sentence, “As with most poisonous substances, less injury, some stimulation, and finally no effect should be obtained with increasing dilution of the heavy water.” I’ve read that sentence probably 50 times and I still don’t understand what it says.
  • I’ll have to think about their results some more, but if they are accurate in their findings, this study may indicate there is some optimal amount of D2O. This is something we have suggested when analyzing the tobacco seed growth when looking at germination rates.
  • They also say that an optimal amount of deuterium may lie somewhere around 1 in 4000. And they state that for growth in bulk low concentrations of deuterium may be a stimulant.
  • This is a fascinating statement, “Until more heavy water becomes available it will not be possible to determine the optimal concentration, the effects on fermentation and respiration, and the extent to which the yeast may be adapted to greater concentrations of the heavy isotope of hydrogen.” It hadn’t occurred to me until just now that this paper was written in 1934, which is just a few years after the purification of D2O! Well I hope I can shed some more light on their original studies, seeing as how the experiment was left unfinished some ~80 years ago.