Strange contaminant in cell culture

[brett]

>Hi
>
>We have been having some problems with our tissue 
>culture 
>which might be a contamination. 
>What we are experiencing is round specks or particles 
>which appear to float around in the medium, they dont take 
>over the dish like a typical bacterial, fungal or yeast 
>contaminant.They appear to have a wiggly movement. We 
>previously thought of it as being cell debri, but its 
>movement led us to believe its bacteria or other 
>contamination. The size seems to be like an average 
>bacterial cocci. Now when looking closely, we have seen 
>thatit also sits on the cell, or possibly seems to be 
>budding from the cells. Black specks can be seen sitting 
>on rounded up (but still adhering) and properly adhered 
>cells. The pathology dept. here at Western Inf., Glasgow 
>have been unable to  culture it on regular medium and at 
>present trying enriched medium. I am not sure but could it 
>be some kind of a protozoan (although the size seems 
>much smaller than a typical protozoa) or some other 
>organism which we are unaware of. and inhabits cells in 
>culture. Another observation we made is that it grows on 
>rat cells better. we actually bought in a batch of NIH3T3 
>cells from ECACC (which we fine before splitting),  were 
>split on arrival and got contaminated the very next day. We 
>regularly use Human Embyonic Kidney 293 cell line, which 
>is also started to play host to this organism.I will 
>appreciate very much if anyne could help us out here.
> Thanks very much
>
>Obaid Khan

I still don't buy that it is an micro-organism. Often small particulate
matter can squirm around due to Brownian motion, and may be mistaken for
bacteria. I have often gazed at CaPO4/DNA ppts and worried needlessly.
If it is an organism, you *do* have a medium with which to culture it:
cell medium (without cells). My guess is it is cell debris. Perhaps your
medium is too rich. I have seen similar things when I use DMEM or alpha-MEM
instead
of MEM. Also, ease back on your FCS, or borrow someone else's from a different
lot. Best of luck.


Brett Lindenbach
    
Program in Immunology                              
Washington University - St Louis                  
brett at borcim.wustl.edu