Biofilms are everywhere on Earth, from dental plaque and pond scum to systems we use to clean up oil spills. Here, biofilms can protect their inhabitants from antibiotics, radiation, temperature changes and other extreme environments that would otherwise kill them almost immediately.

The behaviour of biofilms on Earth is fairly well studied, but we’re only just beginning to figure out how they’d react to alien environments – which is crucial if we are to avoid contaminating other worlds.

Now, an experiment shows that stowing away on a spacecraft may actually help the microbes survive.

Salty and dry

Although Mars is mostly dry, we know its ice caps contain water, and the planet may even have seasonal streams. To examine how biofilms might react to these Martian waters, Adam Stevens at the University of Edinburgh and his colleagues dunked them in seven Mars-like brines with a range of chemical compositions and strengths.

All of the biofilms did well in the weakest brines, lasting well past the 5-hour observation time. As the brines got harsher, though, a divide started to appear: biofilms that were dried out prior to dunking did much better than regular biofilms with their water content intact.

Any biofilms that made it from Earth to Mars would probably be desiccated from the trip through the vacuum of space. It turns out that this arduous ride could actually prepare them to thrive on Mars.

After a momentary shock in the most intense brines, dessicated biofilms started to grow, presumably protecting themselves from their harsh environment. This may have been a consequence of communication throughout the biofilm: a cell on the outside edge of the film, exposed to Mars’s brutally salty brines, could send a warning signal to the insulated cells deeper down. Those cells could either form more goo or reproduce more quickly to build the barrier.

After 5 hours in the most intense brines, which were up to 70 times saltier than the weakest one, all the microbes in the dried-out biofilms were dead. The regular, hydrated biofilms did much worse: in the harsher brines, their cells died within an hour. Some hydrated biofilms were done for in half an hour or less.

Martian microbes

On Mars, areas with water (even salty, briny water) are designated as “special regions” by the international Committee on Space Research. They’re the most likely spots to find Martian life, but also the best places for Earth-based contaminants to thrive. Because any contamination could make it impossible to accurately study the regions, we have to be extraordinarily careful about sending any spacecraft or rovers to these regions.

Biofilms could help Martian microorganisms survive, so they might be something to look for in Mars’ briny recurring slope lineae or in the salty seas of icy moons further out in our solar system. But the danger is that they could also help microbes from Earth thrive, overtaking any previous life and polluting the science.

“This research gives us some information about what we could possibly look for if we do go and investigate these brines – which, on the flip side, we’re saying maybe we shouldn’t,” says Stevens.

“To me, this is a kind of a call to pick up the baton of this area that we really need to understand as we launch into an era of space travel,” says Jennifer Macalady at Penn State University in University Park.

Source: New Scientist