Extremophiles and the Physical Limits of Life on Earth and Beyond'

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Extremophiles and thePhysical Limits of Life
on Earth and Beyond.
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Which of these can be considered an extreme
environment?

• An oxygen-rich atmosphere.
• Salty water
• Basic water (i.e. high pH)
• Outer space
• All of the above

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Which of these can be considered an extreme
environment?

• An oxygen-rich atmosphere.
• Salty water
• Basic water (i.e. high pH)
• Outer space
• All of the above

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• Environment
• Temperature
• Radiation
• Pressure
• Desiccation
• Salinity
• pH
• Oxygen tension
• Chemical extremes
• Vacuum Electricity

Definition growth gt80C Growth 60-80C Growth
15-60C Growth lt15C Weight loving Pressure
loving Cryptobiotic anhydrobiotic Salt loving
(2-5 M NaCl) pH gt9 Low pH loving Cannot tolerate
O2 high CO2, arsenic, mercury
Examples Pyrolobus fumarii -113,
Geobacter-121 Synechococcus lividis humans Psychr
obacter, insects D. radiodurans Shewanella
viable at 1600 MPa Haloarcula, Dunaliella Spirulin
a, Bacillus firmus OF4 (10.5) 12.8?? Cyanidium,
Ferroplasma Methanococcus jannaschii Clostridium H
omo sapiens Cyanidium caldarium tardigrades
Type Hyperthermophile Thermophile Mesophile Psychr
ophile Barophile Piezophile Xerophile Halophile A
lkaliophile Acidophile Anaerobe Miroaerophil Aerop
hile
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Which taxa contain extremophiles?
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Taxonomic Distribution of Extremophiles
Courtesy of Pace lab, 2004
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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!
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In what categories of extreme environments can
Sea Monkeys live?

• Salinity
• Desiccation
• Radiation
• All of the above

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In what categories of extreme environments can
Sea Monkeys live?

• Salinity
• Desiccation
• Radiation
• All of the above

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Examples of extreme parameters
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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.

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Temperature limits for life
sulfur dependant archaea
methane-producing archaea
heterotrophic bacteria
cyanobacteria
anoxygenic photosynthetic
fungi
algae
protozoa
mosses
vascular plants
insects
ostrocods
fish
protozoa
algae
fungi
bacteria
archaea
Himalayan midge and.?
However many organisms, including seeds and
spores, can survive at much lower and higher
temperatures.
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Effect of high temp
Synechococcus
Chloroflexus, 65C
75C
65C
Source, gt 95C
Thermocrinis ruber 83C

• Octopus Spring, Yellowstone National Park

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The new high temp champion Geobacter

• Stops reproducing at 121C, remains stable to
  130C.
• 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

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Antarctica
under the ice-covered lake
preparing to dive under ice-covered lakes
mat layers
lift-off microbial mat
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pH limits for life
heather sedges
Natronobacterium
sphagnum
Bacillus firmus
algae
ephydrid flies
Spirulina
fungi
protists
Synechococcus
Archaea
carp
Sulfolobus
rotifers
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1
2
3
4
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pH
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Zygogonium sp.

• Zygogonium is a genus of filamentous green algae.
  This species is acidophilic.

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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.

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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.
• Dont repair cell damage during desiccation, so
  must be good at repair upon rehydration.

Evaporite, Baja California Sur
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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 Earths
  atmosphere, and thus is newly relevant with
  respect to interplanetary travel or to an
  potential extraterrestrial biota.

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The Solar Spectrum
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Deinococcus radiodurans (Conan the Bacterium)

• An example of survival in extreme radiation
  environment
• Can withstand 1,500,000 rads
• 500 rads kill humans!

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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.

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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

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Examples of extreme ecosystems

• Geysers, vents
• Ice, polar regions
• Subsurface
• High salt
• High oxygen
• Mine drainage
• Nuclear reactors
• Soda Lakes
• Atmosphere

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Space a new category of extreme environment
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Extremophiles beyond Earth
Multiple Mars possibilities
spacecraft meteors comets
?
"biozone in Venusian clouds
European ice ocean
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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)

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Jupiters Moons
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EuropaDark Material Seeping Through Cracks
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Zooming in on Cracks and Flows
10 km
5 km
Ice - sometimes it suddenly cracks, sometimes it
slowly flows
50 km
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Europa models - 4
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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.

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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.

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Titan boulders

• This image shows the ground near the Huygens
  spacecraft.
• The boulders are probably water ice.

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Extremophiles and Mars
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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?

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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 (3108 km3 in volume!)
• Volcanic outgassing could provide several bars of
  CO2

Hauck and Phillips, JGR, 2002
Phillips et al, Science, 2001
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What do you get when you combine heat and a
hydrosphere?
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Volcanic outgassing leads to sulfuric acid

• 4SO2 4H2O 3H2SO4 H2S
• or
• H2S 2O2 H2SO4

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Sulfates on Mars

• 8 wt in soils globally
• Identified from orbit and in situ by the Mars
  Exploration Rovers
• Many probably formed in hydrothermal systems
  early in Mars history.

sulfate salts in disturbed soil
Midway Geyser, Yellowstone
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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 biosignatures.

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A good analog for acid-sulfate weathering
Cerro Negro (Black Mountain), Nicaragua
Lets go there now!
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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 that
  of places on Mars.

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Is Nicaragua safe?
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Cerro Negro
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Inside the crater
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I licked my lips and my tongue started
burning. -Hyneks 2008 Field Notes
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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 its tough.
• Still, Mars had all the necessary materials for
  terrestrial life to survive water, biogenic
  elements, energy sources.

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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.