Microbiologists have traditionally identified pathogens (disease-causing organisms) by growing them in a laboratory dish from a sample of infected tissue. But not all pathogens can be cultured this way. Molecular tools do exist and have been used to identify some new disease organisms, but they have major limitations. But a new microbe-hunting method holds promise for identifying previously undetected disease-causing organisms. The technological tool relies on DNA sequence data compiled in the nearly completed Human Genome Project over the past 10 years. Dana-Farber Cancer Institute researchers already are preparing to use the technique to investigate the causes of mysterious chronic diseases like rheumatoid arthritis, Type I diabetes, atherosclerosis, lupus, multiple sclerosis, and several types of cancer. Undetected, possibly novel infectious agents have been suggested as possible causes of these and other illnesses. “The technique is good for investigating all these chronic diseases of unknown origin,” said Matthew Meyerson, senior author of a report that was published online by the journal Nature Genetics on Jan. 14, 2002. Meyerson is an assistant professor of pathology at Harvard Medical School.