What type of cell culture contamination is this? - large pieces of jelly-like material!! (Feb/22/2006 )
Hi
You guys who've seen enough of different types of biological contaminants in cell culture, please tell me what you think this is that I'm seeing in my HEK293 cells flask, which continues eventhough I replace with new media:
There is no color change of media, no turbidity, no wriggling small organisms smaller than the cells, and the cells do not seem to be much affected (still the usual shape and alive): but I can see very large pieces of jelly-like materials floating around, and also there are huge long (10-20 times the length of one HEK cell) strands of similar soft looking transparent material adhering to the bottom of the flask, which if they remain long enough, grows to resemble a bunch of seaweeds spreading out.
Help, what is this and how to rid the flask of it?
Are you sure these long threads aren't dead/immobile nematode worms?
If not then check the best-before date on your media bottles and associated reagents. Could be some dodgy FBS possibly. Check all the solutions under the microscope, might be contamination in one of those rather tan the culture itself.
I saw that once in my keratinocytes and I never did figure out what it was. I guessed possibly some sort of fungus (slimy stringy texture like spooled DNA, totally transparent and unmoving, appeared as a gob of slime over the cells....couldn't see it until aspirating the medium)
I did not know nematodes could contaminate cultures? eeuuwww. I did toss the cells; no matter what that stuff was, it sure wasn't normal...but it was only the one batch, not in the frozen stocks. we use serum-free media, but we do use serum briefly when passaging...although subsequent batches of cells with the same serum were fine?
if you figure out for sure what it is, let us know?
I'm a gardener, Soluene; I have no problem with worms....but I don't want them in my cell cultures
well, it looks like nematodes are probably not the culprit?
btw, those pictures are really cool 
I did see some of that slimy stuff once and i tossed out everything...cells, media, trypsin everything..
For the thread like thing...i am sorry i do not have cool answers or pix like soulene
but are u sure those are not outside your flasks?? sometimes if there is a scratch or some media residue outside ur flask (on the bottom) it might look like that. Wipe it with 70% ETOH and see if it still appears...
I did not know nematodes could contaminate cultures? eeuuwww. I did toss the cells; no matter what that stuff was, it sure wasn't normal...but it was only the one batch, not in the frozen stocks. we use serum-free media, but we do use serum briefly when passaging...although subsequent batches of cells with the same serum were fine?
if you figure out for sure what it is, let us know?
Hi everyone
I'm real glad to receive your replies, and my verdict now is that it is a fungus, because of its long strands, which I understand now is called hyphae, and the branching seaweed structure is a mycelium. Couldn't find a pic, so I post the diagram below which is kind of similar. No, its not stuck to the bottom of flask, because a number of strands are only partially attached to the flask, with the top part flapping in the media when the flask is moved. And there's shorter ones floating. And some appear parasitic cos they attach to my HEK cell and presumably is living off it. And the source: my media. Very disappointed that having just received these cells from overseas, I contaminated it with my own media. I want to try to salvage it, but unfortunately no one over here has amphotericin (Fungizone). I have detached the cells, spun it down, added clean media and replated it- its much better now but small strands are still around, so I'm thinking hard what next I could do. Suggestions welcome.
that is not the thing that I saw
I am glad you have found the source of your problem! I hope it works OK for you now