Need to move a miniscule load in a microscopic chamber? Scientists have discovered a way to make green algae carry twice their weight in cargo over distances of 20 cm at speeds of up to 200 microns per second. The delivery is guided by light and may some day be used in applications such as removing toxins from polluted water.

Micro mover. Chlamydomonas reinhardtii algae can ferry polystyrene beads over long distances. CREDIT: Doug Weibel

Scientists are increasingly interested in harnessing biological motors for use in micro- and nanotechnology, but recent research has mainly involved taking moving parts out of cells and adapting them for use elsewhere. It's a complicated process that can require protein engineering. So, chemist Doug Weibel of Harvard University in Cambridge, Massachusetts, and colleagues wondered if they could simply use an intact organism as a beast of burden instead.

"These algae are very reliable," says Weibel, who notes that the technique can be repeated many times on the same organism, allowing it to carry multiple loads. He believes that the method may be useful for moving small cargo in liquids, where precision has always been difficult. And in the future, he says, designer beads could be attached to algae to collect particular toxins or bacteria. Weibel's team reports its findings online this week in Proceedings of the National Academy of Sciences.

"I haven't seen anything like this before," says Viola Vogel, a materials scientist at the Swiss Federal Institute of Technology in Zurich. "We have used motor proteins to transport cargos along predefined tracks, but never over distances like this."

--IAIN TAYLOR

Related sites
See a movie of the algae in action
More on Chlamydomonas