By Meg Chen
“Please collect a few spoonfuls of dirt in a ziplock bag and bring the sample with you to the first day of class.“
It’s been a long, yet quick journey. The path from a random soil sample to a beautiful, unique phage feels so unreal. But now that I come to think of it, it must have taken much longer than three months for the first researcher(s) to experiment with different procedures for isolating plaques and develop the most effective one. For example, who came up with the idea of streaking a plaque?
One of the most important things I learned along the way was lab technique. Early on, I would stay past 5 every day, checking my work at each step. Yet I would still end up with contamination. I figured that since there was no way to keep every single phage out of the microcentrifuge tubes, I resorted to methods to eliminate outside phages, such as cleaning my tools with CiDecon before putting my phage solution in and working closer to the flame. One day, I actually worked dangerously close to the flame and burned a hole through my gloves (though the fire went out quickly and did not get to my skin). Even though I successfully eliminated outside phages from my tubes and plates, I realized that I would have to find ways to minimize contamination instead. For example, instead of reaching into the container to pick out microcentrifuge tubes, I learned from Dr. Fisher that I was supposed to dump them out and close them quickly.
I slowly grew accustomed to the method of sterile technique through trial and error, and by the third week, I was out of the lab by 4 most of the time. I still remained skeptical that my plaques all came from phages in my enrichment plating and not from the surrounding air, and I saved 2 plates for each round of streaking and dilution series so that I could go back and re-streak if I run into contamination another time. After putting top agar on my negative control plate, I would shut the lid quickly, sometimes shattering the outside of the petri dishes. I always took one more tube to pick up the top agar with than I actually needed in case I accidentally touched the tip of one tube to a foreign surface. When our whole class experienced contamination due to the old smeg, my plates with top agar and phage buffer alone did not have any contamination even though I had been slightly less careful. This was when I realized that I had been too paranoid all along, and that the chance of my phage coming from the air is lower than what I originally expected.