Extreme Environments 7 September 2016

Extreme conditions Conditions on early earth may have been “extreme” compared to present-day Extremophiles - organisms that thrive in exteme environments –Heat/Cold –Acids/alkalines –High pressures –dessication Conditions on early earth may have been “extreme” compared to present-day Extremophiles - organisms that thrive in exteme environments –Heat/Cold –Acids/alkalines –High pressures –dessication

Temperature Majority of organisms on Earth thrive in the temperature range °C (mesophiles) Usual response to extreme temperatures: –Cold: Formation of ice crystals in the body –Hot: Structural breakdown of biological molecules (proteins and nucleic acids) Disruption of cells’ structural integrity due to increased membrane fluidity Majority of organisms on Earth thrive in the temperature range °C (mesophiles) Usual response to extreme temperatures: –Cold: Formation of ice crystals in the body –Hot: Structural breakdown of biological molecules (proteins and nucleic acids) Disruption of cells’ structural integrity due to increased membrane fluidity Extreme Conditions

Temperature Extreme Conditions

Thermophiles Extreme Conditions Thermophiles live between 50 and 80 °C –Example: Thermoplasma Archaea Lives in volcanic hot springs Hyperthermophiles live between 80 and 115 °C –Example: Sulfolobus No multicellular plants or animals can tolerate >50 °C No microbial eukarya can tolerate >60 °C

Thermophiles First true thermophile discovered in Yellowstone National Park in 1960s > 50 hyperthermophiles have been isolated to date –Many live in or near deep-sea hydrothermal systems (black smokers) First true thermophile discovered in Yellowstone National Park in 1960s > 50 hyperthermophiles have been isolated to date –Many live in or near deep-sea hydrothermal systems (black smokers) Extreme Conditions

Thermophiles: how they cope Since high temperatures change membrane fluidity, adaptation is change of membrane composition Evolution of proteins to better cope w/ high temps Since high temperatures change membrane fluidity, adaptation is change of membrane composition Evolution of proteins to better cope w/ high temps Extreme Conditions

Psychrophiles Supported in frozen environments of Earth Lowest recorded temperature for active microbial communities: -18 °C Found in all 3 domains of life Supported in frozen environments of Earth Lowest recorded temperature for active microbial communities: -18 °C Found in all 3 domains of life Extreme Conditions

Psychrophiles: how they cope Low temps mean decrease in membrane fluidity, so adaptation is adjustment of ratios of lipids in their membranes Prevent water from freezing with soluble compounds that lower freezing temp of water (e.g. thermal hysteresis proteins) Low temps mean decrease in membrane fluidity, so adaptation is adjustment of ratios of lipids in their membranes Prevent water from freezing with soluble compounds that lower freezing temp of water (e.g. thermal hysteresis proteins) Extreme Conditions

Radiation UV and ionizing radiation can do serious damage to DNA –Deinococcus radiodurans can withstand high-dose radiation because it can accurately rebuild its DNA –Also able to cope with extreme dessication, so also a xerophile - thus known as a polyextremophile UV and ionizing radiation can do serious damage to DNA –Deinococcus radiodurans can withstand high-dose radiation because it can accurately rebuild its DNA –Also able to cope with extreme dessication, so also a xerophile - thus known as a polyextremophile Extreme Conditions

pH Most biological processes occur in middle of pH scale (4-8) Acidophile - thrive at –Occur in geochemical activities Sulfur production at hot springs and deep-sea vents –Cope by keeping acid OUT. Evolved enzymes on the front lines that tolerate extreme acidity Alkaliphile - thrive at –Live in soils containing carbonate and soda lakes –Above pH of 8, RNA breaks down, so alkaliphiles maintain neutrality inside cells Most biological processes occur in middle of pH scale (4-8) Acidophile - thrive at –Occur in geochemical activities Sulfur production at hot springs and deep-sea vents –Cope by keeping acid OUT. Evolved enzymes on the front lines that tolerate extreme acidity Alkaliphile - thrive at –Live in soils containing carbonate and soda lakes –Above pH of 8, RNA breaks down, so alkaliphiles maintain neutrality inside cells Extreme Conditions

pH Acidophile - thrive at –Occur in geochemical activities Sulfur production at hot springs and deep-sea vents –Cope by pumping H+ out of cells at a high rate Alkaliphile - thrive at –Live in soils containing carbonate and soda lakes –Above pH of 8, RNA breaks down, so alkaliphiles maintain neutrality inside cells Acidophile - thrive at –Occur in geochemical activities Sulfur production at hot springs and deep-sea vents –Cope by pumping H+ out of cells at a high rate Alkaliphile - thrive at –Live in soils containing carbonate and soda lakes –Above pH of 8, RNA breaks down, so alkaliphiles maintain neutrality inside cells Extreme Conditions Acidic mudpot Acidic mudpot: located in Yellowstone NP, home of Sulfolobus acidocaldarius. Photo courtesy of National Park Service

Salinity Halophiles require high concentrations of salt to live (2-5 times that in seawater) Found in Great Salt Lake, Dead Sea, salterns Can be coincident with high alkalinity environments Survive by producing large amounts of internal solute so as to not lose water via osmosis Halophiles require high concentrations of salt to live (2-5 times that in seawater) Found in Great Salt Lake, Dead Sea, salterns Can be coincident with high alkalinity environments Survive by producing large amounts of internal solute so as to not lose water via osmosis Extreme Conditions Great Salt Lake, UT. Great Salt Lake, UT. Carotenoids seen here are biproduct of halophiles. Photo Courtesy of just_javier on Flickr

Dessication Some organisms survive low-water environments via anhydrobiosis, a state of suspended animation Extreme Conditions

Pressure Undersea pressures are much greater than surface pressures –Boiling point increases with pressure, so liquid water at ocean floor could be 400 ºC –Pressure compresses volume, so peizophiles have increased membrane fluidity so they don’t get “smushed” Upper atmosphere pressures are much lower than surface pressures Undersea pressures are much greater than surface pressures –Boiling point increases with pressure, so liquid water at ocean floor could be 400 ºC –Pressure compresses volume, so peizophiles have increased membrane fluidity so they don’t get “smushed” Upper atmosphere pressures are much lower than surface pressures Extreme Conditions

Oxygen Aerobic metabolism is more efficient than anaerobic, but it kills cells quicker via oxidation Many organisms with aerobic metabolisms combat oxidation with natural anti-oxidants Aerobic metabolism is more efficient than anaerobic, but it kills cells quicker via oxidation Many organisms with aerobic metabolisms combat oxidation with natural anti-oxidants Extreme Conditions

Earth Extremes: possible analogies to other planets Hotsprings The deep sea Hypersaline environments Evaporites The atmosphere Ice, permafrost, snow Subsurface environments Hotsprings The deep sea Hypersaline environments Evaporites The atmosphere Ice, permafrost, snow Subsurface environments Other Worlds

Extremes on other planets If we’ve seen life thrive in extreme circumstances on Earth, why not on other planets? Mars holds most promise What about moons in our solar system: –Europa –Titan –Enceladus If we’ve seen life thrive in extreme circumstances on Earth, why not on other planets? Mars holds most promise What about moons in our solar system: –Europa –Titan –Enceladus Other Worlds

Europa Life exists w/o photosynthesis in the deep ocean Europa has a subsurface ocean Life may exist beneath the surface Life exists w/o photosynthesis in the deep ocean Europa has a subsurface ocean Life may exist beneath the surface Other Worlds

Titan Airborne micro-organisms? Extremes to withstand: –Dessication –Radiation Airborne micro-organisms? Extremes to withstand: –Dessication –Radiation Other Worlds

Mars Host to several extreme environments –Deserts –Ice, permafrost, snow –Subsurface Other Worlds

Mars: ice, permafrost, snow Microbes and algae exist in frozen environments on Earth Maybe not thriving, but microbial survivors could exist Other Worlds

Mars: subsurface environments Best chance of withstanding Martian extremes –No liquid water at surface –Low pressure –CO 2 -rich atmosphere –Only 43% solar radiation at Earth Subsurface provides –Protection –Possible liquid water –Energy source for chemolithoautotrophs Other Worlds

Summary Earth life arose more than 3.5 billion years ago. Our oldest ancestors may have been extremophiles Life has become progressively larger and more complicated, but large organisms are recent: 650 million years Extremophiles live at high and low T, P, pH; high salinity and radiation Earth’s extreme environments resemble other planets