Large, self-propelling microorganisms can be optically trapped with laser beams, a process previously achieved only for smaller motile cells such as sperm and Escherichia coli.

Gregor Thalhammer and his colleagues at Innsbruck Medical University in Austria used two opposing laser beams and a system involving a mirror, prism and lenses to capture a variety of organisms. These included protists such as dinoflagellates and Euglena gracilis, which measures, on average, 50 micrometres in length. The team's technique avoids creating damaging levels of heat. Euglena was held for 13 minutes without showing signs of heat stress. The method could be used to manipulate microbes for imaging, as well as in other experiments, the authors say.

J. Opt. 13, 044024 (2011)