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 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.
