Separating the good from the bad: Two-handed microbes point to new method for isolating harmful forms of chemicals

April 15, 2009

By Denise Brehm
Civil & Environmental Engineering

Scientists at MIT and Brown University studying how marine bacteria move recently discovered that a sharp variation in water current segregates right-handed bacteria from their left-handed brethren, impelling the microbes in opposite directions.

This finding and the possibility of quickly and cheaply implementing the segregation of two-handed objects in the laboratory could have a big impact on industries like the pharmaceutical, for which the separation of right-handed from left-handed molecules can be crucial to a drug’s safety.

While single-celled bacteria do not have hands, their helical-shaped flagella spiral either clockwise or counter-clockwise, making opposite-turning flagella similar to human hands in that they create mirror images of one another that cannot be superimposed.

This two-handed quality is called chirality, and in a molecule, it can make the difference between healing and harming the human body.

“This discovery could impact our understanding of how water currents affect ocean microbes, particularly with respect to their ability to forage for food, since chiral effects make them drift off-course. But it is also important for several industries that rely upon the ability to separate two-handed molecules,” said Roman Stocker, the Doherty Assistant Professor of Ocean Utilization in the MIT Department of Civil and Environmental Engineering, and a principal investigator of the research.

One of the best-known instances of a chiral molecule causing widespread harm occurred in the 1950s, when the drug thalidomide was given to pregnant women to prevent morning sickness. One naturally occurring form—or isomer—of thalidomide reduces nausea; the other causes birth defects. In another commonly used chiral drug, naproxen, one isomer is analgesic; the other causes liver damage.

Stocker and mechanical engineering graduate student Marcos, along with co-authors Henry Fu and Associate Professor Thomas Powers of Brown University, published their findings in the April 17 issue of Physical Review Letters.

In the paper, the researchers describe how they design