The Hunt for Phage

By Evelyn Chiu

I had no idea what I signed up for when I decided to add phage hunting to schedule while browsing through courses back in July. Probably something along the lines of looking at a microscope, furiously prodding at a pile of samples to try to find some phages.

The first assignment that we got for this class was to dig for some dirt. Having taken AP Environmental Science back in high school, digging for soil samples is nothing new to me. Obtaining dirt without a shovel, though, was a new experience. I imagine I was quite a sight, squatting in the sculpture garden furiously smashing at the ground with the blue plastic silverware they gave us on move in day.

Our goal in this class, basically, is to try to isolate a pure phage sample from the soil we got. At first it sounded easy, especially when I was reading over the lab manuals. Filtration, pipetting, plating . . no problem, I’ve done all those before in previous research experience. Except, as I soon found out, what we’re aiming for isn’t all that easy.

What we all want

Some things that we have done these weeks include direct plating, enrichment, and streaking. Lots, and lots, of streaking. Like almost everyone else, my direct plating was a failure and yielded no results. My enrichment culture, however, gave me two plates that I could work with. I then proceeded on with my task to isolate a pure phage by streaking, streaking, and streaking again. Except, I ran into quite a lot of problems. First, it was contaminated top agar. Then, it was cracked top agar. Then contaminated streaking sticks. And of course, the dreaded incidents where there are no plaques present, except for one . . . that always turns out to be an air bubble.

Everytime

After 5 attempts at streaking, I have finally come up with what appears to be a good line of plates that is likely to produce three generations of single phage populations. They’re roughly medium size, with hazy edges and a bull’s eye morphology.

The family tree

Hopefully, my next couple of streak tests will be successful and I will be able to get an isolated and pure population soon. This class has been fun so far, and I am quite excited to see which phage I will end up with, as well as which line our class will ultimately choose.

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