Bacteria Cause Problems for Genetic Research

Arthur T Knackerbracket has found the following story:

A few years ago, some studies were published that aroused considerable interest among researchers in genetics. These studies had examined a particular epigenetic mark, or modification of the DNA that influences how the DNA sequence is used in different cells. This mark had not previously been observed in multicellular organisms. The mark, known as "6mdA," is, in contrast, common in bacteria, where it plays an important role in protecting the bacteria against viruses.

Reports from numerous research groups stating that they had found 6mdA in various animal species, and even in human cells, stimulated not only major interest among the research community, but also some questions. One of these concerned the levels of 6mdA detected, which were so low that scientists wondered whether such a rare epigenetic signal could truly have a function. Following these initial reports, some other published studies were unable to detect 6mdA in animals.

Just as many other research groups, Colm Nestor's group at Linkiping University started to study this puzzling epigenetic signal. They were, however, unable to detect it in human or mouse cells. Eventually, they detected 6mdA in two samples of human cells, but it turned out that both of the samples were contaminated with mycoplasma bacteria. The researchers suspected that the epigenetic mark came from the bacteria and not the human cells. They treated the cells with antibiotics against mycoplasma and saw the 6mdA signal disappear.

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