Although many mycoplasma contaminations of cell cultures remain undetected over many years and thus seem to have no apparent influence on the growth or other characteristics of the cells, this is by far a misinterpretation of the symbiotic relationship of eukaryotic cells and mycoplasmas. Mycoplasmas indeed have a multitude of different effects on the various eukaryotic cells. However, the effects are not constantly seen in all infected cultures, but depend on the mycoplasma species, the type of cell culture, and the cell culture conditions. Nearly every parameter measured in cell culture or experimental investigations may be affected by mycoplasmas (1 ).
