Spore-detecting diving board.

Researchers have demonstrated a new way to detect bacteria. The approach could lead to faster and more reliable detection of virulent microbes in the environment.

Most detection systems capture microbes by using an antibody to bind to a region on a pathogen's surface, says Philip S. Low of Purdue University in West Lafayette, Ind. But these regions aren't usually important to the pathogen's survival, so they often mutate, he says. This renders the detection system ineffective.

Low's group instead designed a protein fragment to recognize a region on a microbe's surface that doesn't typically change. In a pathogen, he says, such a site can't be mutated without the microbe losing virulence. So, there's a much lower chance that alterations in the targeted region will defeat the test, says Low.

The team paints the protein fragment, or peptide, onto a silicon chip frayed at one end into rectangles 500 micrometers ([micro]m) long, 100 [micro]m wide, and 1 [micro]m thick. When these miniature diving boards capture spores, their surface tension changes, causing a deflection that can be measured with a laser, explains Low.

In an upcoming Journal of the American Chemical Society, Low's group reports results for a chip frayed into eight sections--four coated with a binding peptide and four with a nonbinding peptide. The binding peptide captured more spores of Bacillus subtilis, the nonvirulent form of the bacterium that causes anthrax. The researchers confirmed the spores' presence with microscopy.

The group is now testing a peptide specific for the anthrax pathogen Bacillus anthracis.--A.C.