Normalfreezer expt

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The P1 lab is official at Hackuarium (as of 1nov17), and we really want to know if we can get away with using the normal -20 freezer to stock strains.

(If someone would like to help for translations to French or other languages, please do feel free!)

First Test

We wanted to test the method of Cody et al 2008, J Microbial Methods. testing 10% skim milk for stocking bacterial strains vs. the normal 15% glycerol conditions.
The bacterial strain DH5alpha was inoculated on 15oct and grown in LB o/n at 37oC with shaking in LB media.
To note: you should not autoclave milk powder!!

On 16October. Made up 20% milk powder, but did not have sterile filters, so just used it for this test...
Made good 30% glycerol (sterilized no problem, in autoclave - when the milk got carmelized).

Made 2 big Nunc freezing tubes with each combination, 1/2 E coli culture and 1/2 milk or glycerol.
Put all 4 vials into the freezer in a styrofoam chunk to let freeze gradually.

Second Test

On 2 November, streaked out 2 plates with the frozen cultures.
Both grew very well, as seen in the third and fourth images of the gallery below!

Third Test

Did another round of plate streaking on 22nov17 with both '1' vials - glycerol vs milk stock test.
Noticed that the vial for the milk had a 'special' layer at the top (0.4mm)... and this was where I got the innoculum.
Perhaps this stock also grew less well this time - but certainly not sure...
Next time, should take out innoculu frozen, with the loop, as usual, but then let the drop thaw in a sterile tube, so can put the same volumes on the two plates for the streaks.



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