Finding a Phage

Back in April, I came to Hopkins to visit for SOHOP. I’d been accepted, but I still had to make the decision of whether I would move halfway across the country to come to Johns Hopkins, or stay in my home state (was it really that hard of a choice?). So I woke up at 2 a.m. my time to fly out here. Although most of that trip passed by in a caffeine-fueled haze, a few things stood out. Among them was the brightly lit UTL and the number of times my hosts insisted I should sign up for Phage Hunting. And by some luck, I got into the course.

I neglected to collect a soil sample before coming to lab, and I was glad I did. My first day of class featured a field trip to the Phage Gardens. I scooped up a soil sample from under some tomatoes, and we returned to the lab to start working on the samples.

As we started working with the sample, a few things came as a shock. Unlike the C labs of the past, our course was not defined by strict time periods. We could come and go as we pleased, and worked at the pace guided by our progress rather than set deadlines. Furthermore, to keep materials sterile, we had to throw out many things after one use. As I pipetted liquids from one test tube to another, I couldn’t help but watch the pile of waste pile up. Nonetheless, I couldn’t help but be drawn in by the excitement of isolating my phage.

My initial attempts at direct plating yielded putative plaques that turned out to be nothing more than air bubbles. My enrichment sample and dilutions, however, yielded several plaques. All were large, but some were totally clear, some were hazy, and some looked like a bullseye. Next, I started streaking the samples (A, B, and C ) in an attempt to dilute them out. This entailed using several sterile sticks or micropipettes to draw a series of intersecting lines on an agar plate. Although I started the process with three plaques, some disruption in the agar and aggressive phages hindered this process.

Ultimately, I discarded plaques A and C and chose to stick with Plaque B. On my third, and hopefully last streak, however, I found the plate totally clear. This meant the phages had killed all the smeg bacteria (M. Smegmatus is the bacteria used in lab), but it also made it impossible to distinguish each plaque from each other. I redid the streak from the previous plate as well as taking a streak from the totally clear plate. To my surprise, the next streaks revealed small clear plaques rather than the large ones I had seen previously. Unfortunately, this meant that I have to redo the streaking until I receive three consecutive identical plaques. Hopefully, my next round of plaques will isolate soon so that I can start creating stock phages.

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