Algae motors

Dogs fetch. Pigeons deliver messages. Yaks and oxen haul heavy loads.

Now, scientists at Harvard University have found that even tiny algae can be used to do work. Made of just one cell, certain types of algae can drag little objects around, the researchers say. If this skill can be harnessed, algae may someday power tiny machines.

In this algal species, named Chlamydomonas reinhardtii, each rounded cell has two threadlike structures known as flagella, which beat back and forth in a kind of breast stroke to propel the organism.

Algae and other single-celled organisms move with the help of motor-like structures inside their cells. But removing the motors from cells to use them in micromachinery is tough to do. The Harvard scientists, instead, used the whole cells to do work.

First, they created a special molecule with two sticky ends. One end sticks to an algal cell’s body and the other end sticks to plastic. They coated a bunch of tiny plastic beads with this substance.

Next, the researchers put a pile of coated beads in the middle of a track that had been cut into a glass slide. They put a few algae on one end of the track, and they shined a dim light on the other end. Algae are attracted to light, so they swam toward it.

Once the algae got to the middle of the track, they ran into the sticky beads. Each cell picked up one or two of the plastic objects as it kept moving toward the light. Each cell could haul up to its own weight in plastic without slowing down much at all. Some swam as far as 20 centimeters (about 8 inches). That’s 20,000 times the length of their bodies!

Beating its twin flagella, this algal cell lugs a plastic bead through water.

Proceedings of the National Academy of Sciences

To separate the beads from the algae, the researchers shined ultraviolet (UV) light on them, which broke the sticky molecule’s bonds. Then, they used visible light to get the algae to swim away.

Algae will never be as fetching as your pet dog Spot or Fluffy. But they may eventually make your life a bit easier, working on microscopic assembly lines to help construct special microdevices for you and your body.—E. Sohn

Going Deeper:

Brownlee, Christen. 2005. Bitty beasts of burden: Algae can carry cargo. Science News 168(Aug. 20):117-118. Available at http://www.sciencenews.org/articles/20050820/fob6.asp .

You can learn more about Chlamydomonas reinhardtii at www.chlamy.org/info.html (Chlamy Center). You can order materials for science fair projects and classroom lab experiments involving these algae at www.chlamy.org/strains/projects.html (Chlamy Center).