Life in the Deep Subsurface

31 Pages·2005·2.01 MB·English

by  Ann Windnagel

Life in the Deep Subsurface
Steven D’Hondt
University of Rhode Island
NASA Astrobiology Institute
Some key questions
• How big is Earth’s
subsurface biosphere?
• Where does it live?
• What is its composition?
• What are its principal
sources of energy?
• To what extent is it
independent of the
surface world?
D’Hondt 2005
The standard biomass estimate
Continental
Global
Oceanic
Plant(cid:1)
Soil/Aquatic Prokaryotes(cid:1)
Intraterrestrial Prokaryotes(cid:1)
Whitman et al., 1998, PNAS.
D’Hondt 2005
Microbes in deep
sediments
Microbe from deep beneath the Arctic seafloor.
D’Hondt Photo courtesy of D.C. Smith, NAI URI team. 2005
Some are alive
ODP Site 1225, 320 mbsf.
20 μm
Schippers et al., 2005, Nature.
D’Hondt 2005
Prokaryotes in
deep mines
Microbes from an 1130-m deep
borehole (1130-64) at Lupin gold
mine (Canada), sampled during a
2005 expedition organized by the
NAI IPTAI Team (stained with
Cyber Green). The presence of
different morphologies suggests a
diverse microbial community.
) 9 live
n
mi HgCl2-killed
8
/
ml
/ 7
m
dp 6 Microbes from this sample exhibited
(

ty 5 significant hydrogenase activity (Error bars
vi
cti 4 are 95% confidence intervals).
a
e *
s 3
a This may be the first direct assay of
n
e 2
g microbial activity at such a great depth.
o
r
d 1
y
H
0
1130-191 1130-197 1130-64 1130-273
Photo and data courtesy of B. Soffientino, NAI URI team.
Borehole
D’Hondt 2005
How deep does Earth’s life go?
Currently claimed Metabolic
depths status
1.0 km in marine sediment active
2.8 km in continental rock ?
3.6 km in Antarctic ice inactive?
D’Hondt 2005
Microorganisms in some
extraordinary subsurface
environments?
D’Hondt 2005
Prokaryotes
from lake ice
3600 meters
below the
Antarctic ice
surface?
Photomicrographs of prokaryotes
from accreted Lake Vostok ice:
(A) a coccoid-shaped cell,
(B) a rod-shaped cell,
(C) an SEM image of a coccoidal cell
at a magnification of 1.5 x 105,
(D) an SEM image of the same cell
as in (B).
Prokaryotes from this sample
respired (but did not grow) in
Karl et al. 1999, Science.
laboratory radiocarbon experiments.
D’Hondt 2005
Organisms in 250 Ma salt?
Bacterium
Isolation and culture has
been reported of a
bacterium from a brine
inclusion in a 250 Ma salt
deposit.
Sampled salt piece
Vreeland et al., 2000, Nature.
D’Hondt 2005