make the ambergris­substitute.

　　Bohlmann found that gene and took it out of the tree cells. Then he did something that might

　　sound strange to someone who doesn't work in genetics: Bohlmann put the gene from the tree

　　into yeast (酵母) cells.

　　Yeast may sound familiar because it's used to make things like bread, wine and beer.

　　Biologists like to work with yeast because it easily adopts new genes and changes its features and

　　behaviour. When Bohlmann put the fir tree gene into the yeast, the yeast started making the

　　same chemical that had been produced by the tree.

　　Perfumers pay big money for ambergris because it is a fixative, which means it holds a smell

　　in place on a person's body.

　　“Cheap perfumes smell good in the first hour or so and then everything is gone，” explains

　　Bohlmann. “But expensive perfumes are much more stable. Their smell lasts much longer, for

　　hours or even a day after you apply them.”

　　The new chemical, made from the tree genes, can be used as a fixative, too. And using

　　yeast to make it is far cheaper than acquiring ambergris.

　　Bohlmann admits he never thought he'd get into the perfume business. But now, he says,

　　producers have been calling to find out how to use his technology in new perfumes.

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