The Contamination

by Eve Rosekind

My phage hunters experience started out as any other – with dirt. That’s right —  I picked up my dirt sample from the herb garden outside the Fresh Food Café. Following the lab manual, I used part of that sample in my direct plating with no resulting plaques. But there was still hope. I plated my enrichment sample with its many dilutions (100 – 10-4) and waited for a week to see its results. As I looked at my plates, they brought a smile to my face. I gazed down at a beautiful dilution of plaques across my plates. I had phage! As some of my fellow phage hunters can attest to, the exhilaration and excitement felt at the discovery of phage is unsurpassed. I named my phage “Herb” in honor of where I found it. With my Herb in hand, I went to work.

The next step in my phage hunting process was to purify my phage population to make sure there was only one phage. To do this, I picked two isolated plaques from my 10-3 dilution plate and streaked them onto plates: I picked two because it looked like one plaque was smaller then the other, and I wanted to determine if there were two different plaque morphologies on the plate. This process was repeated for two lab periods, with the result of plaques, until that fateful day. The day the bacteria struck.

Now I’m not talking about M. smegmatis that the lab has been working with this whole time. No, some unknown, alien bacteria had contaminated my plates and I wasn’t alone. This invader attacked the plates of my fellow phage hunters as well. At first I thought it was a fluke, no big deal, so I restreaked from my last successful plate of plaques. Alas, this produced the same result – a strange bacteria on my plate and no plaques. Our TA streaked two plates: one of M. smegmatis and one of this unknown contaminate so as to compare them with the bacteria on the contaminated plates. The bacteria on my plate resembled that of the contaminating bacteria.

It was a dismal day in lab when we determined my plate was contaminated. Like many of my classmates, I am attempting to purify my plaques by flooding my last successful plate and filtering the solution it to see if my phage is still present. Even though I have yet to see the results, my hopes are low. If I have to guess, I would say that my phage is to the contaminating bacteria and not to M. smegmatis.

So while I have lost Herb to the contamination, I will always remember Herb fondly. When tragedy strikes, the tough stay strong; therefore, I must continue to push onward in my quest for purifying phage by adopting one on my lab partner’s phages. But let this story be a warning for all of you fellow phage hunters across the country: beware of contamination.

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3 Responses to The Contamination

  1. emilyjanefisher says:

    The contamination hit us hard. Maybe in future years we will isolate phages specific to whatever bacteria are floating around the halls of Macaulay.

  2. I’d only go for the alternate culture if the timing were better. By that I mean if EVERYONE had been nailed by the contamination, then it’s plausible. If that were the case, everyone could switch over to looking for phage against the mystery bug, and we wouldn’t have to worry so much about a contaminant overtaking our stock culture (we certainly wouldn’t have to worry about smeg taking over a culture). But if we had to keep two cultures going, one of which could easily overwhelm the smeg culture? That falls somewhere between tempting fate and being foolhardy.

    While I don’t think the students would necessarily agree, I think the entire experience is pretty close to real research —- shipments don’t arrive on time (uh, not they shipments from HHMI — they arrive ahead of time), cultures get contaminated, top agar fails to harden and slides around, and you can try 8 times and still fail to get a phage. If the impulse, after 8 platings fail, is to set up another, then maybe research is for you.

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