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Cell culture problem - weird stuff grow in my cells - (Feb/01/2003 )

Lately, some weird stuff grow in my cells. They seem to be tiny dark particles floating around. I'm sure they are not bacteria or fungal contamnations because my cells still grown fine. But they make the medium look cloudy. This seems to happen after I trypsinize and split the cells. And these stuff seem to be secreted by cells since their number increase as cells proliferate.
Clearly I can not use these cells for transfection. It really bothers me. Any suggestion or information on this will be greatly appreciated!


Your cells might grow fine even if you do have fungal or bacterial contamination. I strongly recommend doing a gram stain and seeing if there's anything suspicious. However, if you're seeing what looks like little black particles, you may want to check your media formulation. Media made with pyridoxal HCl sometimes forms a black precipitate, and it appears nearly randomly - one bottle from a lot will be fine, another won't. Try to find the media formulated with pyridoxine instead.


what cells are u using now?? it might be due to ur cells isolation procedures whether any filtration being done. if wan further information, u can just tell me the cells u use. might be human skin cells, bone cells etc


Hello there,

It sounds like these little particles could be cell derbis caused by triniziation etc. Try change to fresh media after 1 day of passaging if they disappear.

But, it sound more like a yeast contamination to me (because your media went cloudy!)

I would chuck away all media, start a fresh vial of cells, ask other colleages whether they have any contamination problems in their tissue culture and fumigate the hood (just to be at the safe side)

(it is talking from experience...)

Hope it helps,



How are those cells now? What happened?



I have already seen something like your problems in a culture of REN. Like you say, their numbers continue to grow. We have change all materias (new PBS, new medium,.....) but they were always these dark points. Finally these problem was resolved when we tested an antimycoplasm. Some test kit are availabeld:

"" (french language)

have a nice night tongue.gif (in my GMT)


since the dark particles occurs after trypsinization, you might be over trypsinizing your cells. Over trypsinization cause cells to degrade. Cell degradation causes the proteins to precipitate (black particles) in the medium.