Environmental Engineering Reference
In-Depth Information
outcrop of the sampling site or squeezed from clay matrix with burial. What-
ever the mechanism, our study suggests that the porous ash layers may provide
horizontally distributed microbial habitats in the subseafloor environments that
act as good reservoirs of potentially old viable microbial remnants.
Thermophilic Spore-Formers from the Sediments of the Peru Margin
(ODP Leg 201).
ODP Leg 201, which took place early in 2001 off the coast
of Peru, represented the first ODP mission focused on the microbiology and
biogeochemistry of the deep oceanic subsurface. As with the pelagic clay en-
vironment described for the Sea of Okhotsk, our attempts at cultivation yielded
little in the way of viable cells, despite targeting a wide variety of physio-
logical types of organisms under aerobic and anaerobic conditions at various
temperatures [42]. Curiously, however, from several depths, we were able to
cultivate thermophilic fermenters that grew at 55
◦
C (Table 1). Epifluorescence
microscopic observation of the cells stained with DAPI and fluorescence in situ
hybridization (FISH) with Archaea- and Bacteria-specific probes revealed that
the cells were anaerobic thermophilic spore-forming fermentative bacteria (Fig.
4). Most probable number (MPN) method revealed that the viable population
size of those thermophiles were below 10
2
cell per 1cm
3
of the innermost core
sediment sample (Table 1). Phylogenetic analysis of 16S rRNA gene revealed
that isolates were closely related with
Anoxibacillus flavithermus
and
Bacillus
licheniformis
. Since the growth temperature of isolates was clearly different
from the in situ conditions and the sedimentation age of deep sediments was
approximately 20,000,000 years, it would appear that these members are likely
to be old microbial components that have been transported from either ter-
restrial geothermal or deep-sea hydrothermal fields and then buried in marine
sediments, to be stored as spores for millions of years until clement conditions
allow their germination and growth.
ODP Site
Core section
Depth (mbsf)
MPN population (cells/cm
3
)
1227
Hole A12-3
102,4
33
1228
Hole A2-2
7,0
no growth
1229
Hole A2-2
7,0
no growth
Hole A22-2
186,9
33
1230
Hole A1-2
1,8
66
Hole C2-4
8,5
no growth
Hole A9-2
66,5
83
Hole A15-4
121,5
no growth
Hole A21-3
160,6
14
Table 1.
Population of anaerobic thermophilic heterotrophs in deep marine sediments of the
Peru Margin (ODP Leg 201) estimated by three series of six-tubes MPN method.
