Week 3, Day 3

   May 30, 2013

Today in lab we began by checking the results of our TSIA and indole tests that we were told to re-do last session. The results were the same as before, and after checking with our professor he said there might have been a mislabeled sample giving us a different species. We definitely got the correct genus, which was Proteus. Our sample was labeled as Proteus valgaris, but tested for Proteus inconstans.

Next we moved on to the food purity testing. Our group will be testing the purity in a hamburger extract sample. We prepared a Petri dish with four different holes (one in the center with three surrounding).

Preparing the Plate

 We transferred a drop of the hamburger extract to the center well, and a drop of goat anti-bovine, goat anti-swine, and goat anti-horse albumin one each in the other three holes. We set the plate in the room temperature incubator overnight. This test will allow us to see if the hamburger extract contains beef, pork, and/or horse meats by the reaction that occurs between the hamburger extract and the anti-albumin samples (albumin is a protein found in meat).

Anti-body Albumin Samples

We also completed an HIV antibodies test. We were given a positive sample, a negative sample, and an unknown sample. We transferred 50 μL purified antigen into 9 holes of the microstrip and waited five minutes for the antigen to bind to the plastic walls.

Microstrip

 We then washed the microstrip by dumping out the purified antigen solution and filling the wells with a wash buffer.

Dumping the Wells

Wash Buffer

 We then dumped the wash buffer out and used a pipet to transfer 50 μL of the positive control into three well, the negative control into three wells, and the unknown sample into three wells.

We waited five minutes to allow the serum antibodies in the samples to bind to the antigen before washing them out again in the same manner. We then added 50 μL of secondary antibody into all nine wells and waited 5 more minutes to allow the secondary antibody to bind to the primary antibody.

 We washed the wells out twice before transferring 50 μL of enzyme substrate into all of the wells. After 5 minutes we checked the wells for a blue-ish color, which is the indicator for a positive test. The positive control turned blue while the negative and the unknown sample remained colorless. This indicates that the unknown sample was a negative test for antibodies.

Our professor also showed us how a hand-held UV light can purify bacterial filled water. We prepared a Petri dish with the before sample and after UV light treatment sample and we will check them tomorrow.

The last thing we did for the day was take cooled boiled milk and transferred them into several tubes. We then added some yogurt to each tube and set them in the 37°C incubator. Tomorrow we will observe the bacterial growth in the tubes which will form yogurt.