Algae Chows Down on Other Plants

The green algae Chlamydomonas reinhardtii. CREDIT: Bielefeld University View full size image

When deprived of other food sources, a widespread type of green algae can break down other plant materials and slurp them up as food, a new study finds.

It's the first time that a member of the plant kingdom has been shown to break down another plant's cellulose, the biopolymer that gives strength to plants' cell walls, and use it as an energy source, according to the new research.

Normally, the algae Chlamydomonas reinhardtii uses the sun to turn carbon dioxide and water into the simple sugar glucose, via the process of photosynthesis. But when researchers deprived the tiny cell of carbon dioxide, it cannibalized other plants' materials, said Lutz Wobbe, a researcher at Germany's University of Bielefeld and co-author of the study describing the finding, published recently in the journal Nature Communications.

"Our study for the first time demonstrates that an organism which is capable of performing photosynthesis can digest cellulose as well," he told OurAmazingPlanet.

This trick could come in handy in the production of biofuels like cellulosic ethanol, where expensive enzymes are needed to break down tough cellulose and turn it into simpler sugars that can then be converted to ethanol, Wobbe said. It could also be useful in making biodiesel, since C. reinhardtii is capable of making fats that can be converted into the fuel.

The algae break down cellulose by secreting an enzyme called cellulase, an ability thought to be unique to fungi, bacteria and animals, Wobbe said.

Christoph Benning, a biochemist at Michigan State University who wasn't involved in the research, said the finding wasn't shocking, but hadn't been clearly shown before. "I cannot recall another plant that breaks down cellulose and takes up the sugars," Benning said. "It's not that super-surprising, but I haven't heard anything like it before."

It makes sense that this species could live off of cellulose since it normally lives in the soil, where carbon dioxide and sunlight isn't always readily available, but other plant materials are, said Stephen Mayfield, director of the San Diego Center for Algae Biotechnology.

"The real world is a tough place, it is literally eat or be eaten," he said.  For example, "Two percent of the human genome is dedicated to brain function and 25 percent is dedicated to defense against pathogens (the guys trying to eat us)," he wrote in an email. "That should tell you all you need to know about the world: Everyone is out for a free lunch and it turns out algae is no different."

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