Working on the Weekend – Our Last Weekend in San Lucas!

July 12, 2016:

Who thought staying in for a weekend would end so well? Because we needed to look over samples on Saturday morning and work on Sunday, our team was not able to go along with the other UVA students this weekend. Aurora was a little bummed that we were not able to spend more time with our friends on the weekend in Antigua, but we all knew that the project was more important. Friday night we stayed in and spent some quality team building time. We watched a movie in the common room and send to bed early.

We also had a meeting with Dr. Mills Saturday morning on the most refined version of our lab protocol. He tested his hypothesis himself back in the lab at UVA, showing a positive result with many coliform bacteria growing on the plate. We evaluated the results together, and great news! This protocol works the best.

Here’s what we discovered: We are now able to read the samples with ease, without as many problematic extra air bubbles obscuring the view of valuable air bubbles produced and associated with colonies. We also discovered together, with collaboration, the value in hydrating the plates differently than we were before, with the toothpick method. We discovered that there is a film of dried gel on the upper film that we had not known about prior. When this upper film is hydrated with water, the upper film becomes a gel to seal with the hydrated agar. The joining of the of the two creates a seal where air bubbles can form very visibly associated with colonies. This makes the colonies a lot more distinct and easy to see if there are any.

But with the toothpick hydration, we weren’t allowing the upper film to be hydrated as well. It also took a long time. With this new method, we use 1mL of pure bottled water to hydrate the plates, and then we carefully close the upper film. Then an important step is next: we immediately lift up the film to prevent the seal from forming and the pink lower agar from being torn up onto the upper film. Then we can place the filter paper that has been vacuum filtered with the sample quickly onto the plate, and close the film slowly, to create an almost perfect, air-bubble-free seal every time.

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This is an almost perfect looking water sample test that was done on one of the community member’s filters in Xejuyú. It is very clean, readable, and has very few extraneous air bubbles to obscure the view of any possible colonies. This family not only has a clean working filter, but also is drinking very clean water free of coliforms, since this test was taken from water in the storage container. They are keeping their container clean too.

Normally, the test plates are not used with a filter paper that concentrates the contaminants of larger samples of water onto one paper, but rather with a small sample of 1mL of water and no paper. For our purposes, we wanted to test larger amounts of water, so we had to use different procedure than instructed. That is why the procedure was involved more steps.

After this, we went to the lab in the office after that conference with Dr. Mills very excited to try it on our new samples from earlier in the week. We had to rush over to the lab to make sure that the samples didn’t hit the 48-hour expiration. Thankfully we made it back on time.

We tested about 30 plates on Saturday. We have been working so hard for these last few weeks. On Monday we worked at the foundation. Due to a recent tragic unforeseen death of a San Lucas community member we were instructed to not go to do sample collection. So, we worked for a few hours in the foundation on our final project and wrote some final questions that we want to talk with Lesvia and Elcia about. We then went back to the office after lunch and plated the samples that were brought in for us by Elcia and Lesvia. We plated 22 plates in the office and prepared a plan for tomorrow’s workday. Tomorrow we will go to the communities!

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Our team working hard in the lab!

-Aurora Lofton

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