> Under light microscopy dark dots are visible in the cells and are likely
> to be also moving on their surface. Cell growth, attachment and
> viability are affected.
I had the same thing a few years ago.
> These mysterious creatures are only observed in association with cells
> but not in incubated cell free medium.
> If you have an idea who these intruders could be or have an advice how
> to recognize them or get rid of them please help me.
Hypothesis : mycoplasma (?)
Test : Hoechst staining
Remove : passage in vivo (a few days in the peritoneum of mouse...)