WASHINGTON (AP) - Genes extracted from soil bacteria and slipped into a laboratory microbe have given pharmaceutical scientists a new source of a group of natural compounds that are used to make several major drugs.

The compounds - polyketides - used in drug production are usually made by certain bacteria families. Manipulating the genes in these bacteria to cause them to form particular types of the compounds has led to development of drugs that now account for about $10 billion in annual sales.

Many of the drug compounds are difficult to synthesize, so pharmaceutical companies use natural organisms, such as soil bacteria, to make the drugs in huge, industrial-sized vats.

But some key polyketide-making bacteria are hard and slow to grow, and they also resist the genetic manipulation necessary to make the drugs. This makes industrial production of drug compounds from these organisms difficult and more expensive.

That problem may be solved, according to a study appearing Friday in the journal Science.

Researchers at Stanford University in California and at Brown University in Providence, R.I., have found a way to use a common bacteria, E. coli, to do the work of the more finicky soil bacteria.

The scientists put into E. coli genes from three different soil microorganisms, changed some of the natural genes in E. coli and produced a laboratory culture that churns out polyketides at a high rate.

The work means that E. coli, an easily manipulated bacteria well-known to researchers, could be substituted for the more difficult polyketide-making bacteria, the authors said.

Heinz Floss, a bioorganic chemist at the University of Washington, Seattle, said in Science that the discovery is ``a real breakthrough.''

Co-authors of the study are Blaine A. Pfeifer, Suzanne J. Admiraal, Hugo Gramajo and Chaitan Khosla of Stanford, and David E. Cane of Brown.

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