As I went to passage my cells this morning I had a quick look under the 'scope
and was about to go into the flow hood to look after them, when something made me turn back and have a closer look. Under higher magnification I saw this, which made me swear:
See those tiny little ovals? A couple of them look like Mickey Mouse. They're yeast. Now usually when you get a contamination (and you grow without antibiotics, as is my practice) you find the flask swarming with bacteria the next day, and you can actually see this without a microscope. Occasionally however you can get a yeast contaminant without accompanying bacteria, especially if you work in a lab that uses the little bastards.
Now I could throw in some amphotericin, but actually it's a lot less heartache in the long run to throw away the infected cultures. Fortunately I always keep a back-up, and I split those this morning. They looked clean, but fingers crossed...
And this, children, is why we examine our cell cultures closely every day.
Comments
This is also why I insisted, several years ago, that the guy who was working with yeast in our sibling lab would NOT use out tissue culture room. I got my way, and we didn't have any yeast =)
Posted by: Eva | October 13, 2008 01:32 PM
When I worked in Brisbane, we had a sign on the incubator: "sponsored by Coopers Brewery". Every ceiling panel was ringed with mold, and high concentrations of Pen/Strep were the order of the day.
Now I work in Portland, OR, a much cooler climate, don't use any antibiotics at all and (fingers crossed) have only had a couple of incidents.
But then there was the guy in our lab who cultured lymphoma-derived "T cells" at a fantastic rate, swilling down FBS like it was PBS for six months, before I took a look... and noticed his cells budding. As in, shmoos. Yup, they were yeast all along.
Posted by: bill | October 13, 2008 07:04 PM
Yegods Bill, don't some people have microscopes??
(Why were you using P&S to kill mould?)
Posted by: bk | October 14, 2008 07:45 AM
Good catch -- we had an antimycotic in there as well, but I can't remember what it was (proprietary thingy maybe... not amphotericin anyway).
Posted by: bill | October 14, 2008 12:55 PM
Oh, and Yeast Dude *was* looking at the cultures, every day, quite faithfully -- he just thought the yeast cells were teeny little eukaryotic cells. See, he was trying to establish a line from resected tumors in a mouse lymphoma model, and early on he asked me whether T cells were likely to be smaller and rounder than fibroblasts. All innocent of the horror I was unleashing, I said that yes, that was generally so, and thought no more of it...
Posted by: bill | October 14, 2008 01:07 PM
Fungizone is the common antimycotic—it's just a tradename for amph B.—I don't know what else people might use.
That's really quite an astonishing tale, Bill. I mean, smaller, yes, rounder, probably, but..
ye gods and little fishes. No wonder they grew quickly. No hyphae?
Posted by: bk | October 14, 2008 10:12 PM
having been a palaeontologist has its compensations.
Posted by: Henry | October 14, 2008 10:41 PM
Bill's comment is why I was adament (and annoying) when I first started working with my cells... "What should they look like" didn't really cut it so I forced my lab mates to confirm the phenotype for a few times when I was starting splitting them.
On the other hand, in my old lab there was a graduate student who thought it was Strep on the agar plate - oh no, but it was a nice penicillin resistant Staph though. (Nice yellow tint of the colonies. That was microbiology 101...)
Posted by: chall | October 15, 2008 05:11 AM