Day 6 – Recuperating Day and Refining the Procedure

June 27, 2016:

Day 6 of the project was more of a recuperating day to try to refine our lab procedure so we could continue getting samples later. We met up with Elcia and Lesvia in the morning to go over the new plan of which houses we are going to when and then return to the foundation to Skype with Dr. Mills so he could help us. We brought most of our lab equipment back with us because there is no Wifi in the lab. Dr. Mills was extremely helpful in helping us decide the best way to hydrate the plates. The filter test plates need to be hydrated with clean water before use so that the bacteria can access the nutrients in the medium. In our set up, we use a Buchner funnel and vacuum pump to run 50mL of sample water over a cellulose nitrate filter paper to trap bacteria on the paper that we then place on the agar plate and incubate it to grow coliform colonies. The problem we encountered was then when we placed the filter paper right after hydrating the medium and closed the protective plastic flap; water spilled everywhere and created air bubbles due to an uneven surface. Our goal was the get the medium hydrated without creating air bubbles and trapping water on top of the filter paper that would create condensation between the paper and plastic cover. One strategy had been to hydrate the plates, close the flap, refrigerate them and then open the flap again. But we found that when we did that, the pink agar medium stuck to the upper plastic flap and rendered the plates not as reliable because the nutrients would be on top of the filter paper, not underneath them where they should ideally be. This is what had been done prior to this year. One technique we came up with Dr. Mills using the resources we had was to hydrate the plate, place toothpicks under the flap so it wouldn’t touch the medium and let the water soak in the medium for a couple hours before placing the filter paper. This is the technique we are testing how and hopefully the technique we will move forward with tomorrow.

Sarah Dar_Guatemala1
Per Dr. Mills’ advice, we were using toothpicks to raise the film off of the plate during hydration of the plates.

-Sarah Dar



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