Dr. Cano is well known among molecular biologists for the revolutionary research conducted by a team of which he was a member. He and the other scientists isolated DNA from extinct zebras and other animals and plants, using their analyses of DNA sequences to map relationships among species and evolutionary pathways. Some of their conclusions remain controversial, but their work created a new and fruitful field of biological research.

Dr. Cano is so confident of his latest findings that he has founded a company, the Ambergene Corporation, in San Carlos, Calif., to develop pharmaceutical products derived from the putative ancient organisms. Ambergene has already applied for patents for at least three of the new antibiotics he believes the bacteria have helped him to produce.

These drugs, Dr. Cano said, could fill therapeutic gaps created by the increasing immunity of certain disease-spreading microbes to antibiotics. He and his colleagues reason that pathogenic bacteria that have never been exposed to natural antibiotics that disappeared from the world at large millions of years ago may be vulnerable to them. If so, ancient bacterial antibiotics could become valuable weapons against disease.

Dr. Cano said that most of the ancient microorganisms he had cultured were strains of Bacillus sphaericus, a harmless bacterium common today in soil and in the bodies of insects. Whether or not the strains of Bacillus sphaericus found in amber are essentially identical to modern bacteria remains to be seen; skeptics who contend that they are the same say that this shows the "ancient" bacteria to be nothing more than modern contamination.

But Dr. Cano and his former graduate student Dr. Monica K. Borucki said that they had found slight but significant differences between the DNA of the ancient, amber-sealed Bacillus sphaericus and that of its modern counterpart. The small genetic differences could be explained as the result of evolutionary change over 30 million years, during which modern Bacillus sphaericus diverged from its ancient form, he said.

Skeptics point out, however, that the slight genetic difference might also be explained in terms of normal variation between individual bacteria. Biologists are likely to argue over this point for some time.

Asked if ancient bacteria extracted from amber and introduced into the modern world could pose a health hazard, Dr. Cano replied, "This is certainly an issue we've had to address."