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Topic Name: Brown Chemists Explain the Origin of Soil-Scented Geosmin
Category: Agricultural
Research persons: DAVID CANE, PHD
Location: Brown University, Providence, RI 02912, United States
Details
Brown University chemists
have found the origins of an odor – the sweet smell of fresh dirt. In
Nature Chemical Biology, the
Brown team shows that the protein that makes geosmin – source of the good earth
scent – has two similar but distinct halves, each playing a critical role in
making this organic compound.
“Everyone is familiar with the wonderful smell of warm earth,”
said David Cane, professor of chemistry at Brown who oversaw the research. “Now
we know precisely how it is made.”
Geosmin, which literally translates to “earth smell,” was
scientifically identified more than 100 years ago. In soil, bacteria produce the
chemical compound. In water, blue-green algae make it. Along with the pleasant
scent of warm, moist soil, geosmin is also responsible for the muddy “off” taste
in some drinking water. That is why the substance is of interest to water
purification experts and even vintners, who want to keep the benign but pungent
substance out of their wine.
Until recently, scientists knew little about how geosmin is
made. Then, a few years ago, Cane found the gene responsible for geosmin
formation in
Streptomyces coelicolor, a strain of plant-munching bacteria found in
soil. Last year, the team discovered that a single protein converts farnesyl
diphosphate to geosmin.
In their new work, Cane and his lab team found that this
protein, called
germacradienol/geosmin synthase, folds into two distinct but connected
parts, similar to a dumbbell. One piece is responsible for the first half of the
reaction, cranking out a chemical that wafts over to the companion bit of
protein, which then produces geosmin.
“We found that geosmin is created by this bifunctional enzyme,”
Cane said. “The two steps of the process that forms geosmin are
metabolically
related. This finding was a real surprise. This is the first bifunctional enzyme
found for this type of terpene, the class of chemicals geosmin belongs to.”
Jiaoyang Jiang, a Brown graduate student in the Department of
Chemistry and lead author of the journal article, said microbiologists working
in water purification plants will be most interested in knowing the origins of
geosmin. By understanding precisely how the substance is synthesized, Jiang
said, these experts may find a way to block it – avoiding the foul taste that
keeps people away from the tap.
“Geosmin may smell good in the garden, but not in the glass,”
she said.
Xiaofei He, a former Brown graduate student, contributed to the
research. The work was funded by the
National Institute of
General Medical Sciences.
About Researcher:
DAVID CANE, PHD
Professor
Chemistry
Phone: +1 401 863 3588
E-mail: david_cane@brown.edu
David Cane's Brown Research URL:
http://research.brown.edu/myresearch/David_Cane
Brown University, Providence,
RI 02912
About Brown : http://www.brown.edu/
Related Online Resource:
Good earth- Chemists show
origin of soil-scented geosmin
ScienceDaily- Origin of soil-scented geosmin discovered
Chemists show origin of soil-scented geosmin
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