possible contamination of a cell culture? - (Apr/05/2006 )

Can anybody help me with a piece of advice? My cell culture smells unpleasantly (as by bacterial contamination); no visible signs of a contamination could be detected however. The cell morphology as well as growth parameters are not changed. Knows anyone the possible reason?
Thanks in advance for any hint.

Are you growing the cells in a flask/dish? Check under 400x objective and look for motile black rods or dots that zoom around like frantic ants. At low contamination, or for slow-growing strains of bacterial contaminants, you won't see visible changes in medium indicator color or turbidity. But you will still see many motile bugs at high power.
Some fungal contaminations also smell bad. You may want to look out for filamentous structures (hyphae) that look adherent or messy and clumped together.

Thanks for the suggestion,

I have not found anything resembling Bacteria or fungi in the culture itself as well as in agar plates yet; Mycoplasmentest is negative too. The culture seems to be O.K. now. So I can only guess what has happened. Probably it was false alarm.

Thank you anyway