EMBARGOED FOR RELEASE:
Thursday, 19 July 2001 at 14:00 U.S. Eastern Time
Scientists identify methane-consuming
microbes from ocean depths
MOSS LANDING, CaliforniaóMonterey Bay Aquarium Research Institute (MBARI)
microbiologists report in the 20 July 2001 issue of the journal Science
on new techniques that combine the identification of microorganisms
with their biogeochemical activity. In the study, the researchers used the
new approach to identify marine microbes that
consume methane, an important greenhouse gas.
Methane oxidizing archaeal and bacterial aggregate
methane seep sediments visualized using confocal microscopy.
"The method is providing a new window into the microbial world.
Now itís possible to determine both the identity and function of
naturally occurring microbes, at the level of single cells. We donít
even have to grow them in the laboratory to do it," said Ed DeLong,
leader of the research group.
"Until recently no one knew which microbes were involved in the
oxidation of methane in anoxic marine sediments," adds Victoria
Orphan, first author of the Science paper. "By combining
molecular and stable isotope techniques, we found a way to link specific
microbes to this important ocean process."
In collaboration with Christopher House of Pennsylvania State
University and researchers from Woods Hole Oceanographic Institution and
the University of California, Los Angeles, the MBARI group used a remotely
operated vehicle to collect marine sediments from deep sea methane seeps
in the Eel River Basin off California. Molecular probes were used to
identify archaea and sulfate-reducing bacteria in the sediments. These
microorganisms, 0.5 to 2 micrometers in diameter, can live without oxygen
and have not been grown in culture. First the scientists applied RNA
probes, then they used secondary ion mass spectrometry to determine stable
carbon isotope ratios of the individual microbe cells and cell aggregates.
This method distinguished microbes that use methane as a carbon source
from those using carbon derived from photosynthesis or other organic
The researchers showed that the archaea and bacteria cells could be
identified individually within the cell aggregates. The two kinds of
microbes form a partnership to extract energy from methane in the absence
of oxygen. The methane-oxidizing archaea at the core of the aggregate
transfer carbon compounds to their sulfate-reducing bacterial partners in
the outer layers of the aggregate. Since nearly 80 percent of the methane
in marine sediments is removed by these methane-consuming microbes, the
discovery provides new insight into a critical process.
Orphan and her colleagues are excited by the implications of this
research, as these techniques can be used to simultaneously identify
environmentally important microorganisms and characterize their metabolic
activities in nature.
Related paper: Nature 398: 802-805, 29
Related news item: Nature 407: 577-579, 05 October 2000
Debbie Meyer, 831-775-1807, firstname.lastname@example.org
related to this release.