ADVANCES
22 Scientific American, December 2020SYNTHETIC BIOLOGY
DNA Glow
Bacterial machinery unlocks
new water-pollution test
Pollution from industry, agricultural runoff,
pharmaceuticals and other sources con-
taminates water around the world, and
detecting it can be expensive and time-con-
suming. Now researchers have developed a
quick, potentially inexpensive way to test for
at least 16 dangerous contaminants, includ-
ing lead, copper and antibiotics, according
to a study published in Nature Biotechnology.
The test takes cues from bacteria, which
are especially adept at reacting to specific
contaminants. “Nature has been solving this
problem for billions of years,” says study co-
author Julius Lucks, a chemical and biologi-
cal engineer at Northwestern University.
His team searched the literature to find out
which proteins bacteria produce to deal
with various pollutants. The researchers’
new, handheld testing device takes advan-
tage of these proteins’ reactions using a
series of vials: each has a freeze-dried solu-
tion that incorporates a specific protein,
which causes the mixture to glow green
when an added drop of water contains a
particular contaminant.
Each solution includes custom-engi-
neered strands of DNA with one section
that a pollutant-sensing protein is bound to
and another section that generates a fluo-rescent glow if activated. The solutions also
contain RNA polymerase, which makes
RNA by following a DNA strand. If the pro-
tein bound to the DNA encounters its corre-
sponding contaminant, the protein changes
shape and falls off. This lets the RNA poly-
merase travel all the way along the DNA
strand, making the sample fluoresce green.
The study is “a really nice, clever and cre-
ative use of synthetic biology and highlights
what the field can do well,” says Mar y Dun-
lop, a synthetic biologist at Boston Universi-
ty, who was not involved in the research.
Researchers have used a similar meth-
od to detect pathogens, but this device is
the first to identify so many pollutants,
Lucks says. The test is “very promising,”
says Susan Richardson, a University of
South Carolina chemist, who focuses on
water issues and was not in volved in the
research. She cautions, however, that it may
need to react to lower contaminant concen-
trations before it can be widely useful.
— Susan CosierIllustration by Brown Bird DesignI TA LY
Scientists have examined a shark found south of Sardinia
that somehow survived to three years old without skin or
teeth. They concluded it was a genetic mutation and plan to
check nearby sediment for potential pollutant causes.GREENLAND
Climate researchers discovered records
of an automatic weather station that
measured –93.3 degrees Fahrenheit one day
in December 1991—a temperature colder
than the average on Mars and the coldest
ever recorded in the Northern Hemisphere.For more details, visit
http://www.ScientificAmerican.com/dec2020/advancesPANAMA
A tropical forest ground survey revealed that one
lightning strike often damages more than 20 trees,
a quarter of which can die within a year. Researchers
combined this finding with satellite data to estimate
that lightning kills 200 million tropical trees worldwide
every year—a significant cause of their demise.AUSTRALIA
A new study shows how
Australian grasslands’ strange
barren patches—called fairy
circles—are landscaped by
the grasses themselves.
Baking heat creates a hard clay
crust over a patch of ground;
water runs off of it, forming a
more welcoming zone at its
edges that grasses bolster as
they grow and cool the soil.CHINA
Newly discovered and
pristinely preserved fossils
suggest two sleeping
dinosaurs were buried alive
in an underground burrow
125 million years ago. The
burrow may have collapsed
under volcanic debris.IN THE NEWSQuick
Hits
By Sarah Lewin FrasierU.S.
Western Joshua trees will get a year
of temporary endangered species
status in California while the state
considers permanently listing
the distinctive succulents as the
first-ever plant species protected
because of climate change–related threat.
Testers add a drop of water to each vial;
when viewed in the device, vials glow when
the water has their assigned contaminants.