Crude
oil and gas naturally escape from the seabed in many places known as
"seeps." There, these hydrocarbons move up from source rocks through
fractures and sediments towards the surface, where they leak out of the ground
and sustain a diversity of densely populated habitats in the dark ocean. A
large part of the hydrocarbons, primarily alkanes, is already degraded before
it reaches the sediment surface. Even deep down in the sediment, where no
oxygen exists, it provides an important energy source for subsurface
microorganisms, amongst them some of the so-called archaea.
Splitting
oil into methane and carbon dioxide
This microbe, an archaeon
named Methanoliparia, transforms the
hydrocarbons by a process called alkane disproportionation: It splits the oil
into methane (CH4) and carbon dioxide (CO2). Previously, this transformation
was thought to require a complex partnership between two kinds of organisms,
archaea and bacteria. Here the team from Max Planck Institute for Marine
Microbiology and MARUM presents evidence for a different solution.
During
a cruise in the Gulf of Mexico, the scientists collected sediment samples from
the Chapopote Knoll, an oil and gas seep, 3000 m deep in the ocean. Back in the
lab in Bremen, they carried out genomic analyses that revealed that
Methanoliparia is equipped with novel enzymes to use the quite unreactive oil
without having oxygen at hand.
With
the combined enzymatic tools of both relatives, Methanoliparia activates and
degrades the oil but forms methane as final product. Moreover, the
visualization of the organisms supports the proposed mechanism: Microscopy
shows that Methanoliparia cells attach to oil droplets.
Methanogenic
microorganisms have been important for the earth's climate through time as
their metabolic product, methane, is an important greenhouse gas that is 25
times more potent than carbon dioxide.
See:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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