cell line contaminated by something... - (Oct/11/2012 )

I'm working on A549 cell line and Adenovirus. A month ago, I found that A549 cells were growing with weird particles looked like very little virus. But A549 cells were growing well and didn't show CPE from that contamination. I revived cell stock which I got from the other person. Also, I changed all media and its ingredients. The cells didn't grow with that weird particles but after two passages, those particles appeared again. Please give me any comments if you have an idea. Thanks in advance.

if you can include a pic of the particles that might help

Hmmm, it could well be mycoplasma, but you need an incredibly high level of them in the culture (and a sharp eye) to spot them by light micoscopy. It could be that you are seeing sub-cellular components such as the endoplasmic reticuluum, which tend to be more visible when the cells are stressed (I don't know why).