Week 7: Results!

This week was a great week as I had my first really great result from the nitric acid digestions I have been working on. The nitic acid digestion is a procedure that allows us to digest the soft tissue of chironomids and other plant species leaving only diatom frustules. The end result provides clear and easily-identifiable diatoms from the chironomid guts. Our first nitric acid digestion trial with the May samples using a single chironomid did not provide good results. There were likely two problems with the first run. First, we used baking soda to neutralize the acid, which was initially dissolved in solution. However, we had a large white precipitate on our slides at the end, which suggests that the baking soda precipitated out of the solution when evaporating. The second problem was the amount of acid we used. Dissolving one chironomid in 20mL of acid and 20mL of water was too much liquid, and even though the chironomid was dissolved, we did not see any diatoms in the final product, likely because the gut contents were so dilute. 

Correcting for both of these problems, we did a second digestion later in the week, where we dissolved three chironomids from each June sample in 4mLs of nitric acid solution. We did not use baking soda to neutralize the solution. The final product was a clear coverslip covered in diatoms. This was a very exciting result as these slides with the gut contents are permenant slides, and will be available for use for years to come. Now we simply need to finish digesting the May and July samples to have permenant slides for all months and all sites. 

Next week, I am hoping to begin some PCR work to see what kind of DNA is in the chironomid gut. I want to see if our DNA extractions from chironomids can give us useful information about wha they eat. I hope to test for the presence of diatoms, reed canary grass (an invasive species), and another prevelent plant species (TBD). In order to do this, I needed to search for primers for these species. It was fairly straight-forward to find diatom primers because Tawyna Peterson, my PI, helped us find the papers. I then tried to find primers for the reed canary grass, and I believe I found a paper with several primer options. Hopefully those will work and we can order them early next week! I'm very excited to do some of this PCR work because it will help determine the presence/absence of species other than diatoms.