Researchers at the University of Delaware are examining tiny worms
that inhabit the frigid sea off Antarctica to learn not only how these organisms
adapt to the severe cold, but how they will survive as ocean temperatures
increase.
The National Science Foundation study, led by Adam Marsh,
associate professor of marine biosciences in UD’s College of Earth, Ocean, and
Environment, also will compare the process of temperature adaptation in the
polar worm, known scientifically as Capitella perarmata, with that of a close
relative that inhabits temperate waters, Capitella teleta.
“By comparing
these two marine species, we hope to assess how a polar environment shapes
responses to environmental stress,” says Marsh. “By better understanding how the
environment can trigger genetic changes – through the genes the polar worm turns
on or ‘expresses’ – we can gain insight into the potential impact of global
warming on marine ecosystems.”
Arriving in late August at McMurdo Station
on Ross Island, Antarctica’s largest outpost, Marsh and his research team
undertook a series of dives in the freezing waters over the next two months to
collect the polar sea worms, which are segmented like earthworms but belong to
the class known as “polychaetes.”
At a mere half-inch long and no thicker
than the lead in a No. 2 pencil, Capitella perarmata would be a challenge to
collect even on dry land. Because the worms feed on organic matter, the
researchers have found the most abundant concentrations in the top layer of
sediment from McMurdo Station’s old sewage outfall. The divers collect buckets
filled with sediment, from which the worms are sieved.
Just getting to
the underwater site takes some doing, as UD doctoral student Annamarie
Pasqualone points out. Pasqualone, who is from Medford, N.J., stayed on to
complete the experiments in Crary Laboratory, McMurdo Station’s science
building. She will depart the frozen continent before Christmas to travel back
to Delaware.
“A three-foot-diameter hole needs to be drilled through
about seven feet of ice, and then a heated dive hut must be placed over the
newly drilled hole in order to prevent it from freezing over -- and to keep the
divers happy when they surface out of the seawater, which is at a temperature of
minus one degree Celsius,” she says.
Pasqualone has been assessing the
worms’ physiological and biochemical responses as they acclimate to an increase
in environmental temperature from -1.5 degrees C to 4 degrees C in laboratory
experiments. Additional experiments are under way in Marsh’s lab at UD’s Hugh R.
Sharp Campus in Lewes.
For this project, the Marsh laboratory is focusing
on identifying epigenetic changes in DNA methylation in these worms – in other
words, how the environment is influencing the worms’ genetic code. DNA
methylation is a process in animals and plants where environmental signals are
“imprinted” on genes in a genome by chemical modification of cytosine—one of the
bases of the DNA code—to 5’-methyl-cytosine. By tracking changes in metabolic
activity and locating genes where methylation changes are active, the scientists
will be able to pinpoint the types of genes involved in the temperature
acclimation process.
Marsh says he hopes the results of the study will
shed light on the ability of some Antarctic species to survive current levels of
ocean warming.
“The coastal waters around Antarctica have been at very
stable temperatures for millions of years,” Marsh says. “This low-temperature
environment has led to the evolution of many endemic polar marine species. As
global sea-surface temperatures rise, temperatures in Antarctica will also
increase. For animals that are used to constant cold conditions, even slight
increases in temperature can have large impacts on survival.”
Data
yielded by the study on how extreme environmental conditions help shape genes
and proteins also could have important economic applications.
Marsh and
colleague Joe Grzymski at the Desert Research Institute in Nevada recently
co-founded Evozym Biologics, a startup company, to accelerate the discovery of
useful proteins for developing new antibiotic drugs and biofuels. The catalyst
was their respective research on other Antarctic “extremophiles”—soil microbes
for Grzymski and Antarctic sea urchins for Marsh.
“This information has a
huge potential for commercial use in the field of synthetic biology,” Marsh
notes. “Many of the industrial-scale processes that utilize enzymes require that
these proteins are synthetically designed to work efficiently under extreme
conditions. In bioreactors, for example, conditions of high heat or high acid
are common and require bioengineered proteins for increased stability and
catalytic efficiency.”
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