Co-Authors:
Marcus, M., Department of Genetics, Hebrew University of Jerusalem, Jerusalem, Israel
Lavi, U., Department of Genetics, Hebrew University of Jerusalem, Jerusalem, Israel, Agriculture Research Organization, Volcani Center, Bet Dagan, Israel
Nattenberg, A., Department of Genetics, Hebrew University of Jerusalem, Jerusalem, Israel
Rottem, S., Department of Clinical Microbiology, Hebrew University Hadassah Medical School, Jerusalem, Israel
Markowitz, O., Department of Clinical Microbiology, Hebrew University Hadassah Medical School, Jerusalem, Israel
Abstract:
Mycoplasmas are common contaminants of animal cells in cell cultures 1-3. About 25 Mycoplasma and Acholeplasma species have been identified as cell culture contaminants but the most frequent are Mycoplasma hyorhinis, Mycoplasma orale, Mycoplasma arginini and Acholeplasma laidlawii 3. These species are responsible for almost 85% of the contaminations in cell cultures3. We have devised a method for the selective killing of mycoplasmas in contaminated cell cultures, based on the differential nucleic acid metabolism of mycoplasma and mammalian cells. Mycoplasmas are unusual in that they have a nutritional requirement for nucleic acid precursors which can be met by purines and pyrimidine bases or by nucleosides 4-6. Mammalian cells, on the other hand, incorporate very little free pyrimidines7,8 and for that reason incorporation of free bases such as uracil has been used to detect mycoplasmas in contaminated cell cultures 9. One of the free base analogues which can be incorporated selectively into nucleic acids of mycoplasmas is 5-bromouracil (5-BrUra). Visible light induces breaks in 5-BrUra-containing DNA10 and this photosensitivity can be greatly increased by binding of the fluorochrome 33258-Hoechst to DNA11. Its unusually high content of A + T makes the mycoplasma DNA3 an excellent candidate for the induction of breakage by the combined action of 5-BrUra, 33258-H and light because 33258-H has a high affinity for A-T base pairs and an even higher affinity for A-BrUra base pairs12. We report here that treating them in this way provides a practical and simple method for the selective killing of contaminating mycoplasmas; they are probably killed by the breakage of their DNA. © 1980 Nature Publishing Group.