Weird low-light bacteria could thrive on Mars

When grown in far-red light, this cyanobacteria, with the name <em>Chroococcidiopsis thermalis</em>, you may still have photosynthesis, where others falter.

(T. Darienko/<a href=””>CC-BY-SA-4.0</a>)

An international team of scientists has demonstrated that a strange type of bacteria can turn light in the fuel in incredibly dim environments.

Similar bacteria may one day help humans colonize Mars, and expand our search for life on other planets, researchers said in a statement released with the new work.

Organisms called cyanobacteria absorb sunlight to create energy, releasing oxygen in the process. But until now, researchers thought that these bacteria could absorb only specific, higher-energy wavelengths of light. The new work shows that at least one type of cyanobacteria called Chroococcidiopsis thermalis — who lives in some of the world’s most extreme conditions — can absorb redder (less energetic) wavelengths of light, allowing it to thrive well in dark conditions, such as deep under water in the hot springs. [Extreme Life on Earth: 8 Bizarre Creatures]

“This work redefines the minimum energy that is needed in the light to drive photosynthesis,” Jennifer Morton, a researcher at the Australian National University (ANU) and co-author of the new work, said in the statement. “This type of photosynthesis can also happen in your garden, under a rock.” (In fact, a related species has also been found in live rocks in the desert.)

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By studying the physical mechanism behind these organisms’ absorption abilities, researchers are learning more about how photosynthesis works — and increase the possibility of the use of similar low-light organisms to generate oxygen in places like Mars.

“This may sound like science fiction, but space agencies and private companies around the world are actively working to achieve this ambition into reality in the not-too-distant future,” Elmars Krausz, study co-author and professor emeritus at ANU, said in the statement. “Photosynthesis can, in theory, be used with these types of organisms to create air for humans to breathe on Mars.

“Low-light-adapted organisms, like the cyanobacteria that we have studied, can grow under rocks and may survive in the harsh conditions on the Red Planet,” Krausz added.

The researchers originally thought that a particular pigment chlorophyll, called chlorophyll f, has helped the capturing of light, but could not directly participate in the conversion into energy, according to the new work, which was released yesterday (14 June) in the journal Science. But this research shows that, in fact, the pigment takes part in the energy-conversion, and allows the organism to pull the energy of a longer wavelength than ever observed.

“Chlorophyll adapted to absorb visible light is very important for the photosynthesis for most plants, but our research indicates the so-called ‘red’ chlorophyll as critical components in photosynthesis in low-light conditions,” said Morton.

Not to mention, it can play an important role in the search for life beyond Earth: “Searching for the signature of the fluorescence of these pigments can help to identify alien life,” she said. Knowing of such organisms exist on Earth not only broaden where we look for alien organisms, but also suggests what to look for when we look.

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