These nucleic acid-based methods make it possible to identify microbes that are associated with a disease, but in many cases the microbes are uncultivable.

The issues here go well beyond this particular study and H.I.V. Scientists are rapidly identifying disease-causing genes and new microbes.

Using Dr. Pace's methods and others developed in the 1980's, researchers could identify new microbes in a few days.

Lawrence K. Altman, M.D., the medical correspondent and columnist of The New York Times, reported a few years ago that "Many otherwise obscure places have been immortalized by the custom of identifying microbes and diseases by the geographic area in which they were first recognized."

Many waterworks around the country are aging and vulnerable to breakdown, and health experts are urging more research to find new ways to identify and remove dangerous microbes from drinking water.

"We've needed some way to identify microbes after they are set free," said Dr. Margaret Mellon, a molecular biologist and attorney at the National Wildlife Federation, an environmental group that has previously voiced concern about Government regulation of biotechnology.

Many otherwise obscure places have been immortalized by the custom of identifying microbes and diseases by the geographic area in which they were first recognized.

About 1.2 million units, or 9 percent of those collected, were not used for a variety of reasons; for example, because laboratory tests identified contaminating microbes or the designated safe period expired.

Tricorder The Lab-On-a-Chip Application Development Portable Test System (LOCAD-PTS) used by astronauts on the International Space Station is designed specifically to biochemical molecules with the purpose of "identifying microbes on space station services" through use of the Gram Staining Method.