Unless you’re a biologist, the bacterium Mycoplasma probably will not strike fear in your heart. Our mouths are teeming with this tiny and usually harmless microbe. But when Mycoplasma finds its way into a petri dish of cells, it becomes a big and expensive headache. A new study finds that 11 per cent of samples in gene-expression studies were contaminated with Mycoplasma, potentially invalidating those results and wasting millions of dollars.
Coaxing cells — whether it be heart cells or cancer cells or immune cells — to grow in pure cultures is a cornerstone of biomedical research. It’s delicate work that requires careful attention to sterility, lest bacteria or even other cells from the lab drift in and take over.
When it comes to contamination, Mycoplasma is pretty much the worst. The bacteria are so tiny it’s impossible to see them growing. And because they lack a cell wall, they can’t be killed off with a dose of common antibiotics. It’s a problem as old as cell cultures, but we still haven’t found a totally effective way to deal with it.
A new study took a pretty clever approach to studying how widespread Mycoplasma actually is. Instead going into labs to test individual cultures, they hit up a database of existing DNA sequences from other labs. The 9395 samples from 884 projects were tied to papers from top journals like Cell and Nature. Of them, 11% had enough Mycoplasma DNA to look like contamination.
The studies in this roundup were all looking at how expressions of different genes changed due to various factors supposedly under the researchers’ control. When Mycoplasma takes over a cell culture, it gobbles up food and space, stressing out the cells you actually want to study and leading to all kinds of unrelated gene expression changes. That’s not to say the result of every study with contamination is invalid, but it’s certainly troubling.
To get rid of Mycoplasma, you basically have to throw out all your contaminated cultures (along with months of work, if you’re unlucky). Special antibiotics can also sometimes be used. Preventing Mycoplasma contamination really just comes down training humans to be careful, as boring as that sounds. Remember, our mouths are full of these bacteria, which can easily spray out when we’re talking.
It’s pretty much like trying to rid your house of pests. You can clean and clean, but a small lapse will bring them back swarming. And when it comes to biology research, the damage adds up to hundreds of millions of dollars. [Nature News]
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