The
bottom of a glacier is not the most hospitable place on Earth, but at
least two types of bacteria happily live there, according to
researchers.
The
bacteria—Chryseobacterium and Paenisporosarcina—showed signs of
respiration in ice made in the laboratory that was designed to simulate
as closely as possible the temperatures and nutrient content found at
the bottom of Arctic and Antarctic glaciers, said Corien Bakermans,
assistant professor of microbiology, Penn State Altoona. She said that
carbon dioxide levels in the laboratory-made ice containing the
bacteria, which were collected from glaciers in Greenland and
Antarctica, indicated that respiration was occurring at temperatures
ranging from negative 27 to positive 24 F.
Bakermans,
who worked with Mark Skidmore, associate professor of geology, Montana
State University, determined the level of respiration by measuring the
amount of carbon dioxide in the laboratory-made ice.
While
humans obtain energy from sugar, the bacteria in this experiment used
acetate, a form of vinegar. Like human respiration, the microbes take in
the molecules, extract energy from them and breathe out carbon dioxide
as a waste product.
Bakermans
said the study may have implications for the search for life on other
planets, like Mars, because some places on Mars are in the same
temperature range as the temperature levels recorded during the
experiment.
“Although
there are a lot of other factors involved for life to take hold on
other planets,” Bakermans said, “we can still say that if microbes on
Earth can do this, then there’s the potential, at least, that microbes
can do this on Mars.”
Glaciers
and ice sheets represent large ecosystems that cover more than 10% of
the Earth and contain approximately 78% of the world’s fresh water.
The
researchers, who reported their findings in a recent issue of
Environmental Microbiology Reports, said that respiration was reported
at all temperatures examined.
The
respiration rate of the microbes increased as the temperature rose.
While the respiration rates of the bacteria are slow compared to the
human respiration, the microbes could maintain cell structure and
viability throughout the observed temperature range.
The
researchers also performed a staining test to measure cell viability.
When cells are alive or dead, they leave a chemical footprint of those
states. By applying stains to the bacteria in the laboratory-made ice,
the researchers can find those chemicals and determine if the cells are
alive and healthy.
Bacteria
seem to grow best in cracks and crevices within the ice, Bakermans
said. The cracks in the ice create channels that allow water and
nutrients to circulate.
“It’s
hard for nutrients to be exchanged in the ice,” Bakermans said. “But
these channels appear to give the microbes access to nutrients.”
The
bottom of glaciers may be more hospitable for the microbes than other
parts of the glacier because the areas draw warmth and nutrients from
the earth, Bakermans said.
The National Science Foundation supported this study.
