Yogurt Lab Discussion....

On Wednesday, June first, our class started the Yogurt Lab. We began with four test tubes...
The first had only milk in it (negative control), the second had milk and yogurt (positive control), the third had yogurt and ampicillian and the last contained E.coli.

After the first three test tubes were inoculated with a pure culture of suspected pathogen using an "inoculation loop", and the E.coli was inoculted with the E.coli pathogen, we mixed them up using the vortex, which we all had fun with! The next thing we did was to make sure everything was labeled and then we put them in the water bath at 37 degrees celsuis, in order to keep them at a constant warm temperature to maximize our results,and to see how the bacteria progressed when we returned the next morning,

Results: The next day.... We removed the test tubes from the water bath and looked at our changes. The first test tube (with only milk) had a chunky white formation at the top and a clear liquid throughout, the milk had, as a general defintion, curdled. The second test tube, with milk and yogurt had a white fluid, the third (yogurt and ampicillian) was a clearish liquid. I predict the reason that no solid was formed was because ampicillian is a beta-lactum antibiotic, which attacks the cell walls of bacteria, not allowing them to continue their growth. The last test tube had E.coli in it, this tube was the tube that by looking at it, you knew it smelled and we each bravely smelled it, determining the foul smell of rotten eggs. This test tube was a milky liquid also. After this we tested each tubes ph;
#1-ph 6
#2-ph 6
#3-ph 7
#4-ph 6
Our control test tube, containing the yogurt had a ph of 4.
 A video of our results/procedure in action is below:
http://www.youtube.com/watch?v=vVhIArPkyi0

By infecting each tube with bacteria, we found out that the "yogurtness" disease could be spread through contact with the bacteria.

Possible sources of error, a substance not being infected by the yogurt enough, a temperature issue involving the water bath, and an incorrect reading of the substances ph, could all contribute to errors in the experience.