2007 Annual Report - jamstec japan agency for marine-earth ...

polar lipids and DNA from sediment samples from various
parts of the world, including core samples to a depth of 365m
below the sea bottom taken off Shimokita, Japan by the deepsea
drilling vessel Chikyu in 2006, and clarified the fact that
many of the microbial living cells included in sea-bottom sediments
are archaea (Lipp, Morono, Inagaki & Hinrichs, Nature,
2008).
Because archaea cells have a membrane structure with
lower fluidity than bacteria, it is thought that they evolved by
adapting to an environment with a low energy supply rate, that
is, the environment provided by seafloor sediments.
In research on the sub-seafloor biosphere, accurate detection
of the cells in core sediment samples and evaluation of
their quantities is extremely basic and important knowledge.
However, in visual observation by fluorescence microscopy, it
is difficult to distinguish between the fluorescence emitted by
the cells and that emitted by the sedimentary material, and the
limit concentration for detection is high due to the limitations of
identification by the human eye and the amount observed.
Therefore, at the current point in time, it is not possible to carry
out research exploring the limits of the sub-seafloor biosphere,
targeting low biomass environments in future deep environments
and high temperature environments. We developed a revolutionary
new experimental system for accurately detecting
and quantifying only living organisms (cells) containing DNA
from the matrix of sedimentary materials by constructing a
computerized automatic microscope control system and performing
image analysis on the fluorescent spectrum of the fluorescence
microscopy images obtained with that system
(Morono, Terada, Masui & Inagaki, submitted to Nature
Methods). Using the newly-developed technique and microscope
system, the quantity of microbial cells contained in core
samples of ODP Leg 201, which was the world's first subsurface
biosphere drilling voyage, and cores taken off Shimokita
were accurately evaluated based on objective digital data,
reconfirming the existence of large quantities of microbial cells
in deep sub-seafloor sediment samples.
Researchers from the Geomicrobiology Group also sailed
on the Stage 1 expedition (IODP Epx. 315, 316) in the Nankai
Trough Seismogenic Zone Experiment (NanTroSEIZE) and
directly took core samples at multiple drilling locations, including
a mega-splay fault and a fault zone at the leading edge
(frontal thrust) of an accretionary prism. These samples are
being stored in a cryogenic environment in a freezer or in an
anaerobic refrigerator by this research group. Present work
includes measurement of the biomass in Nankai trough drilling
samples using the newly-developed automatic microscope system
and analysis of the diversity of microorganisms using a
first riser test of the Chikyu, which was conducted off
Shimokita in 2006, this research group made an evaluation, by
the culture method and molecular biology techniques, of the
microbial phase in the circulation mud fluids before and after
riser drilling. This research is only possible in the first trial.
This study yielded important knowledge, including the fact that
the current chemical composition of the mud fluids does not
adequately control the multiplication of external microorganisms,
and designated subsurface microorganisms multiplied in
the mud fluid tank after circulation (Masui, Morono & Inagaki,
Geomicrobiol. J. 2008). In the future, detailed studies will be
carried out, including a further quality evaluation of microbial
samples, development of an aseptic sampling method with
frozen samples, and a quality evaluation using different storage
methods.
3 Core Sampler Curation System and Start of Full-Scale
Operation of Facilities and Equipment
The Kochi Institute began receiving of drilling cores for
the ocean areas for which Japan is responsible, as agreed by the
IODP-SPC (Integrated Ocean Drilling Program-Science
Planning Committee), and began preparations to receive core
samples obtained by JAMSTEC's vessels, and other devices.
During this fiscal year, legacy cores with a total length of
approximately 84 km, which were taken by the Glomar
Challenger and JOIDES (Joint Oceanographic Institutions for
Deep Earth Sampling) Resolution under the Deep Sea Drilling
Project/Ocean Drilling Program (DSDP/ODP), and had been
managed by storage facilities in the United States, were succesmetagenomic
technique, etc. in order to determine what kinds
of linkage may exist between the distribution and functions of
microorganisms in sub-seafloor environments and the distinctive
features of organisms accompanying geological activity.
In the future, if the sub-seafloor biosphere is to be explored
by large-depth drilling, evaluation of contamination in samples
by external microorganisms accompanying riser drilling will be
important. Taking advantage of the opportunity provided by the
Photo Hydrated methane gas bubbles.