ITS OVER!!

I am so happy/relieved that this week is over.

On Monday, we checked our 26 strains which were plated on optimal media that contained starch (to see if they hydrolyzed starch). We tested this by pouring 1 mL of iodine (which is a dark color) on the plates. If a clearing appeared on the plates, this meant that the organism does hydrolyze starch (a positive test). If the iodine stayed dark throughout the whole plate, we counted it as a negative test. If the strain hydrolyzes starch, this means that it is capable of producing amylase, which aides in the breakdown of starch. Iodine binds to the starch on the plates and when there is a clearing on the plate around the iodine, this means that there is no starch left in the media (in other words, the bacteria used it all up). Below is an example of a positive and negative starch hydrolysis test:

Strain 11 - starch hydrolysis positive:

Strain 45 - starch hydrolysis negative:
On Monday, we also looked at the plates on which we had plated selected colonies that resembled Modestobacter species (from our Gobi soil sample dilution plates. 10 colonies were selected from the unirradiated plates and 10 colonies were chosen from the 5 kGy irradiated plates). Of these 20 types of colonies that we plated, we attempted to isolate DNA from 12 of them. Therefore, we followed the protocol from the MoBio kit in order to extract DNA from these colonies. On Wednesday, we spent half of the class period taking our midterm. I am so glad it is over!!! The rest of the class period was spent spotting our 26 strains (10 microliters of each strain) on optimal media of pH 4, 5, 6, 7, 8, 9, 10. We put up to 6 strains on each plate. This took a good bit of time and our group was very careful in doing this task. After we spotted these plates, we parafilmed them, and placed them in the 25•C incubator