s
and the
Physical
Limits
of Life on
Earth …and
150
100
50
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
0
pH
-50 ° C
Which of these can be considered
an “extreme” environment?
A) An oxygen-rich atmosphere.
B) Salty water
C) Basic water (i.e. high pH)
D) Outer space
E) All of the above
Which of these can be considered
an “extreme” environment?
A) An oxygen-rich atmosphere.
B) Salty water
C) Basic water (i.e. high pH)
D) Outer space
E) All of the above
Environment
Temperature
Radiation
Type
Definition
Examples
Hyperthermophgrowth >80°C
ile
Growth 60-80°C
Pyrolobus fumarii -113°,
Geobacter-121°
Thermophile
Growth 15-60°C
Synechococcus lividis
Mesophile
Growth <15°C
humans
Psychrobacter, insects
Psychrophile
Pressure
Weight loving
D. radiodurans
Barophile
Pressure loving
Desiccation
Piezophile
Shewanella viable at 1600 MPa
Salinity
Xerophile
Cryptobiotic;
anhydrobiotic
pH
Halophile
Salt loving (2-5 M
NaCl)
Spirulina, Bacillus firmus
Alkaliophile
Oxygen tension
Acidophile
Anaerobe
Miroaerophil
Chemical
extremes
Vacuum
pH >9
Low pH loving
Cannot tolerate O22
Haloarcula, Dunaliella
OF4 (10.5); 12.8??
Cyanidium, Ferroplasma
Methanococcus jannaschii
Clostridium
Homo sapiens
Aerophile
high CO22, arsenic,
mercury
Cyanidium caldarium
tardigrades
Which taxa
contain
extremophile
s?
Taxonomic
Distribution of
Extremophiles
Courtesy of Pace lab, 200
Why study extremophiles?
• Biodiversity of planet
Earth. Origin of life?
• Mechanisms of
survival
• Biotech potential
• Future use in space
Limits for life in the universe … for
example, Mars!
In what categories of extreme
environments can Sea Monkeys
live?
A) Salinity
B) Desiccation
C) Radiation
D) All of the above
In what categories of extreme
environments can Sea Monkeys
live?
A) Salinity
B) Desiccation
C) Radiation
D) All of the above
Examples
of
extreme
parameter
Temperature: what
difference does it make?
➛ Solubility of gases goes down as
temperature goes up.
➛ Organisms have upper temperature
limits.
Chlorophyll, proteins and
nucleic acids denature at high
temperatures.
➛ Enzymes have optimal temperatures for
activity; slow down at low temperature
➛ Low temperature water freezes. Breaks
membranes etc.
Temperature limits for life*
150
sulfur dependant archaea
methane-producing archaea
100
0
mesophiles
50
heterotrophic bacteria
cyanobacteri
a
fung
algae
i
mosses
anoxygenic
photosynthetic
protozo
a
vascular plants
fish fung
i
alga
e
insects ostrocods
protozo
a
bacteri archaea
a
Himalayan midge and….?
-50
* However many organisms, including seeds
and spores, can survive at much lower and
higher temperatures.
Synechococcus
Effect of high temp
°C
5
6
~
s,
u
x
e
l
of
r
lo
°C
h
5
C
7
Source, > 95°C
65°C
T he
rubermocrin
r ~8 is
3°C
Octopus Spring, Yellowstone National Park
The new high temp champion:
Geobacter
• Stops reproducing at
121°C, remains stable
to 130°C.
• Found in black smoker
in Juan de Fuca Ridge,
nearly 1.5 miles deep
in the Pacific.
• Reduces ferric iron to
ferrous iron and forms
the mineral magnetite
Antarctica
under the ice-covered lake
preparing to dive
under ice-covered
lakes
lift-off microbial mat
mat layers
pH limits for life
heather
sedges
Natronobacterium
sphagnum
Bacillus firmus
algae ephydrid flies
Spiruli
na
protist
s
rotifer
s
fungi
Archae
a
Sulfolobus
0
1
2
Synechococcu
s
carp
3
4
5
6
7
pH
8
9
10
11
12
13
14
Zygogonium sp.
Zygogonium is a genus of filamentous green algae. This species
is acidophilic.
Salinity
• Halophiles: 2-5 M salt
• Dunaliella salina is used
in biotech industry.
Produces glycerol and
b-carotene.
• The bacterial halophiles
have been flown in
space.
Desiccation (drying up)
• Can be correlated with
salinity tolerance.
• Possibly a few organisms,
e.g. lichens in the some
deserts, can survive on
water vapor rather than
liquid water.
• Don’t repair cell damage
during desiccation, so must
be good at repair upon
rehydration.
Evaporite, Baja
California Sur
Radiation
Radiation
• Some forms of radiation have been a constant for
organisms over geological time, whereas others
vary seasonally and diurnally. Exposure may
depend on ecology.
• Some radiation is blocked by the Earth’s atmosphere,
and thus is newly relevant with respect to interplanetary
travel or to an potential extraterrestrial biota.
The Solar Spectrum
wavelength (m)
0
1
2
3
4
5
1
0
10
10
10
10
radio waves
10
1
10
2
10
3
microwaves
10
4
1
0
5
10
6
infrared
10
7
8
UV
1
0
10
9
10
10
10
11
10
1
0
12
γ − rays x-rays
Deinococcus radiodurans
(Conan the Bacterium)
• An example of
survival in extreme
radiation
environment
• Can withstand
1,500,000 “rads”
• 500 rads kill
humans!
High oxygen
 Oxygen is the one environmental
extreme that we consider “NORMAL”
 This is one of the WORST
environmental extremes.
 Conclusion: WE are extremophiles too.
What is oxidative damage?
 Oxidative damage is caused by reactive oxygen
species and cause damage to DNA, enzymes and
lipids.
 Can be formed by UV sunlight.
 Oxygen and the OH- radical directly modify DNA
including causing strand breakage.
 Oxidative damage may cause many diseases.
 Protection includes antioxidants and enzymes
Examples of extreme ecosystems
• Geysers, vents
• Ice, polar regions
• Subsurface
• High salt
• High oxygen
• Mine drainage
• Nuclear reactors
• Soda Lakes
• Atmosphere
Space: a
new
category of
extreme
environme
nt
Extremophiles
Extremophiles beyond
beyond Earth
Earth
Multiple Mars possibilities
spacecraft
meteors
comets
"biozone” in Venusian clouds
European ice & ocean
?
Why is life beyond earth
difficult?
 Differences in atmospheric composition
 Altered gravity
 Space vacuum
 Temperature extremes
 Nutrient sources (e.g., organic carbon,
nitrogen)
 Different radiation regime (solar and
cosmic)
Jupiter’s Moons
Europa
Dark Material Seeping
Through Cracks
Zooming in
on Cracks
and Flows
10 km
5 km
50 km
Ice - sometimes it
suddenly cracks,
sometimes it slowly
flows
Europa models - 4
Land O
lakes?
• This image of
the south pole
shows white
clouds and an
intriguing dark
feature with a
sharp boundary.
• This is likely a
lake of
hydrocarbons.
River to the shore?
• This composite
of three images
shows what
looks like a
branching river
draining to a
shoreline.
• Rainfall on
Titan would
presumably be
liquid methane.
Titan ‘boulders’
•This image
shows the ground
near the Huygens
spacecraft.
• The ‘boulders’
are probably
water ice.
Extremophiles
and
Mars
Mars as an extreme
environment
• Temperature: nippy.
• Radiation: Mars is 1.5 AU, so overall solar
radiation is 43% of Earth.
• Oxidants: Realized presence of oxidants
after Viking.
• Liquid water? Past, periodic, hydrothermal
activity?
Ancient Mars
• Magmatism and
volcanism were
dominant processes.
✻ Heat flow out of
early Mars was
high.
✻ The majority of the
Tharsis volcanic rise
was built by 3.7 Ga
Hauck and Phillips, JGR, 2002
Phillips et al, Science, 2001
What do you get when you
combine heat and a
hydrosphere?
Volcanic outgassing leads to
sulfuric acid:
4SO2 + 4H2O = 3H2SO4 + H2S
or
H2S + 2O2 = H2SO4
rocks
Sulfates on Mars
• ~8 wt% in soils
globally
• Identified from orbit
and in situ by the
Mars Exploration
Rovers
• Many probably
sulfate salts in disturbed soil
Midway Geyser, Yellowstone
Sulfates and Biology
• Early terrestrial biota relied upon
chemical energy from disequilibria.
• Redox of sulfur compounds can be
energetically advantageous.
✻ Sulfur metabolizers have been
implicated in the origin of life on
Earth.
• Sulfates can preserve organics and
A good analog for acid-sulfate weathering:
Cerro Negro (Black Mountain), Nicaragua
Let’s go there now!
Cerro Negro, Nicaragua
• One of the youngest
volcanoes in the world.
✻ Erupts about every 6
years.
• Fumaroles are belching
out sulfur-rich steam.
• The chemistry of the
altered rocks are like
Is Nicaragua
Sure, just followsafe?
these simple rules:
Cerro Negro
Inside the crater
“I licked my lips and my tongue started burning.”
-Hynek’s 2008 Field Notes
Habitability
• Volcanoes like Cerro Negro (and
similar enviros on Mars) present
many challenges for biology
✻ low pH, high temp, high sulfur,
limited water, high salinity,
limited nutrients, and short
timescale.
(for Mars add in a high impact
flux early on)
✻ Certainly organisms can survive,
but it’s tough.
Conclusions
• Life has evolved in extreme
environments, many of which have
only recently been uncovered.
• The ancient Earth was a different
place. Extreme for us, but in some
ways more benign.
• The study of extreme environments
on Earth informs the search for
habitats for life on Mars and beyond.