The GluYeast project
Students at FdV Bachelor, this week we made the GluYeast project, a one week project on the chemical gradients. It consists in studying the growth of yeasts (Saccharomyces cerevisiae) in function of glucose concentration and compare our result with an electronic glucose sensor. Yeasts are microorganisms often used in science because they are easy to manipulate and to cultivate, we know their genome and so one... Moreover, yeasts are present everywhere in our everyday life as in the bread or in the alcohol like beer. The glucose is also a very interesting element because it is a molecule essential to the survival of organisms but it also could be toxic when it is in high concentration.
Our purpose is to observe what is the impact of the glucose on the yeast growth like in this video (with a different protocol) or in this article and to compare this biological sensor with a diabetic device testing several glucose concentration diluted in pig’s blood (cf fig 1).
Fig1: Picture during experiments
Fig 2: Representation of experimentation
To start with, we prepared five solutions of YPD (rich media for yeasts) with different concentrations of glucose: 0 g/L, 1 g/L, 20 g/L, 50 g/L and 100 g/L. We have put 100mL YPD per concentration. We also put in culture yeasts during a night. Then the next day, we used a 96 well-plates to put yeasts in culture in a various solutions of YPD. In every well, we added some oil to avoid that the cultures dry out. We realized 14 replicates per concentration (cf fig.2).
Fig 3: Representation of 96 well-plates
Finally, we placed the 96 well-plates in the spectrophotometer, in order to measure the absorbance. We put the device at 30 °C and realized measures every 30min during 10h. From these results, we were able to determine the yeasts growth speed for each concentration of glucose.
Fig 4: Sketch of experimentation on electronic sensor
For our second experiment with the diabetes monitor, we also realized five solutions of pig's blood with different concentrations of glucose, which are the same that for yeasts. Then, after the preparation of these solutions, we just need to realize our measures putting a drop of blood (with a spatula) on the strip inserted into the device. We have changed the strips for each measure (cf fig4).
After this experiment, our results shown that the more the concentration of glucose raise, the more the yeasts growth is important. Note that this results isn’t true for a glucose concentration of 100g/L. Because the glucose can be toxic for yeast above a concentration. The glucose thus plays an important role in the development of yeasts.
With our diabetic monitor, we observe that more the concentration which was put is high, more the measured value by diabetes monitor is also high.
However, the monitor gives a value below the real value. We realized our measures without respecting a waiting time after put the glucose in the blood. Thus the glucose did not necessarily have enough time to dilute itself completely in the blood. Furthermore, the device cannot measure concentrations of glucose higher than 6g / L. That force us to realize dilutions of the blood. That is why the device for diabetic is precise only for small concentrations of glucose.
To conclude, we can say that the glucose is important for the growth of yeasts but it can be toxic in too important concentrations. The diabetes monitor is precise and accurate until 6 g/L of glucose in blood. After this concentration, the device can’t measure the concentration because it’s not it using (diabetic people don’t have this Glycaemia rate of glucose in our blood because it’s really toxic). To improve this project, it would be necessary to realize more replicates for every experiments and by using several strain of yeasts and other devices for diabetics to reduce the biological noise and to have more precise results.
Nevot Adèle, Bouissou Amélie, Jousset Isabelle and Hermant Loïc
L2 students from LFDV
If you want to know more about yeast and glucose, here are some interesting links, that are our ressources:
Article:
Other :
http://www2.ac-lyon.fr/etab/lycees/lyc-69/bernard/IMG/pdf/TPdef_Le_foie_un_des_organes_cles_dans.pdf
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