Small, Cold, and Hungry: Ultra-Small Microbes from a 120,000-Year-OldGreenland-Glacier Ice Sample (Forwarded)

Office of Public Information
Eberly College of Science
University Park, Pennsylvania

CONTACTS before 22 May and after 27 May:
Vanya I. Miteva: (+1)814-865-3330 (lab phone and fax),
Jean E. Brenchley: (+1)814-865-3330 (lab phone and fax),
Barbara Kennedy (PIO): (+1)814-863-4682,

CONTACTS from 22 May to 27 May:
Press Room at American Society for Microbiology meeting: 504-670-4240
Barbara Kennedy (PIO): (+1)814-863-4682,

26 May 2004

Small, Cold, and Hungry: Ultra-Small Microbes from a 120,000-Year-Old
Greenland-Glacier Ice Sample

The discovery of millions of micro-microbes surviving in a 120,000-year-
old ice sample taken from 3,000 meters below the surface of the
Greenland glacier will be announced by Penn State University scientists
on 26 May 2004 at the General Meeting of the American Society for
Microbiology in New Orleans, Louisiana. The discovery is significant
because it may help to define the limits for life on Earth as well as
elsewhere in the universe, such as on cold planets like Mars.

According to Penn State researchers Vanya I. Miteva, research associate,
and Jean E. Brenchley, professor of microbiology and biotechnology, the
majority of the microbes they discovered in an ice-core sample taken from
the glacier were less than 1 micron in size -- smaller than most commonly
known bacteria, which range from 1 to 10 microns. In addition, a large
portion of the cells appeared to be even smaller and passed through filters
with 0.2-micron pores. The scientists are interested in understanding how
microbial life can be preserved in polar ice sheets for hundreds of
thousands of years under stresses that include subzero temperatures,
desiccation, high pressures, and low oxygen and nutrient concentrations.
Because the ice was mixed with the ancient permafrost at the bottom of
the glacier, the microbes could have been trapped there for perhaps
millions of years.

"We are particularly interested in the formation of ultra-small cells as one
possible stress-survival mechanism, whether they are starved minute
forms of known normal-sized microbes or intrinsically dwarf novel
organisms, and also whether these cells are able to carry on metabolic
processes while they are so highly stressed," Miteva says. Physiological
changes that accompany the reduction of a cell's size may allow it to
become dormant or to maintain extremely low activity with minimal
energy.

"Many of these ice-core microbes are related to a variety of ultra-small
microorganisms from other cold environments that have been shown to
use different carbon and energy sources and to be resistant to drying,
starvation, radiation, and other stress factors. Their modern relatives
include the model ultra-micro bacterium Sphingopyxis alaskensis, which
is abundant in cold Alaskan waters," Brenchley reports. She and Miteva
are in the process of closely examining all the microbes they found in
order to determine the identities and diversity of the species and to look
for ones with novel functions.

The researchers used a variety of methods including repeated sample
filtrations, electron microscopy, and a modified technique of flow
cytometry to quickly reveal the number of cells and to estimate their
different sizes, DNA content, and other characteristics. Miteva and
Brenchley discovered cells with many different shapes and sizes,
including a large percentage that were even smaller than filter-pore sizes
of only 0.2 microns. "It appears that these ultra-small microbes often are
missed in research studies because they pass through the finest filters
commonly used to collect cells for analysis," Miteva says.

Scientists believe these dwarf cells belong to the "uncultured majority"
because they are among the 99 percent of all microbes on Earth that never
have been isolated and cultured for study. Obtaining such "isolates" is
necessary in order to describe a new organism, study its cell size, examine
its physiology, and assess its ecological role. "We now know just the tip of
the iceberg of all the microbes that exist on Earth, and it generally is
believed that a large portion of these unknown microbes are very small in
size," Miteva says.

"A major challenge is to develop novel approaches for growing some of
these previously unculturable organisms," Brenchley says. "At present, no
single established protocol exists and little is known about the recovery of
these stressed and possibly damaged cells from a frozen environment that
subjects them to severe conditions for long periods." Some of the cells that
Miteva and Brenchley were successful in cultivating required special
conditions and up to six months to form initial colonies. The researchers
discovered that these colonies grew more rapidly during further cultivation
and that most continued to form predominantly small cells.

"Our study of the abundance, viability, and identity of the ultra-small cells
existing in the Greenland ice is relevant to discovering how small life-
forms can be; how cells survive being small, cold, and hungry; and what
new tricks we need to develop in order to cultivate these small cells,"
Miteva says. "This study is part of the continuing quest by microbiologists
to overcome the current limitations of our methods and to answer the big
question, 'What new microbes are out there and what are they doing?'"

This research was supported by the Department of Energy (Grant DE-
FG02-93ER20117) and the Penn State Astrobiology Center (NASA-Ames
Cooperative Agreement No. NCC2-1057).

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IMAGE CAPTIONS:

[Image 1:
http://www.science.psu.edu/alert/Images/ice9503_5.a.jpg (177KB)]
Material from a 120,000-year-old Greenland Glacier ice sample showing
micro-microbes (small white oblong forms) and larger materials.

[Image 2:
http://www.science.psu.edu/alert/Images/icemicrobes.jpg (191KB)]
One of the novel micro-microbes isolated from a 120,000-year-old
Greenland Glacier ice sample.