英語聽力文摘 泥土的芬芳

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The Smell of Dirt

A lot of people love that fresh-dirt smell. The surprising thing, though, is that it isn’t coming from the dirt itself. Microbiologists have traced the pleasant odor to an organic chemical called “ geosmin“.”

No way! But how does geosmin get into dirt?

A microbial geneticist named Keith Chater at the John Innes Center in England has traced geosmin down to a common bacterium called Streptomyces coelicolor. He even found out exactly which gene in the little critters causes them to produce geosmin.

No way! A bacterium is producing the chemical that smells so good?

Interestingly enough, there are unconfirmed reports that animals are attracted to fresh dirt in the desert, and go there looking for water. As they nose around the dirt, they pick up plenty of S. coelicolor, which then hitch a ride from one oasis to the next.

If it’s true, then the bacteria in general may create the odor in order to attract animals. The animals find water, the bacteria are spread, and everyone is happy.

不少人喜歡聞新鮮泥土的芬芳，出人意料的是芬芳不是來自泥土本身，微生物學(xué)家尋根溯源，發(fā)現(xiàn)宜人的香味是來自有機(jī)化學(xué)物：土臭素。

這不可能!土臭素怎么鉆進(jìn)泥土的呢?

Keith Chater 是英國John Innes中心的一名微生物遺傳學(xué)者，他發(fā)現(xiàn)一種常見的叫藍(lán)色鏈霉菌的細(xì)菌可以分泌土臭素。他甚至還能確定藍(lán)色鏈霉菌中哪種基因產(chǎn)生土臭素。

沒可能啊!細(xì)菌能分泌好聞的化學(xué)物質(zhì)?

有趣的還不止這個(gè)，有報(bào)道還稱沙漠動物就是靠新鮮泥土的芬芳尋找水源，不過有待考證。動物們找尋綠洲的同時(shí)，成為大量藍(lán)色鏈霉菌的媒介，搭載藍(lán)色鏈霉菌游曳綠洲間。

如果藍(lán)色鏈霉菌普遍散發(fā)香氣吸引動物，動物尋找到水源;而藍(lán)色鏈霉菌也能因此繁衍，這不是雙贏嗎?

geosmin：土臭素

Streptomyces coelicolor：藍(lán)色鏈霉菌