The Extremophiles

Typical conditions on Earth today are comfortable for typical present forms of life. Average Temperature - 20 to 36°C (-4 to 97°F) Pressure - 1 atm (sea level) to 0.5 atm (5500m) Salinity - Oceans are 3.5% salt pH - Neutral (pure water) to slightly Basic (sea water) Radiation - Low levels = 0.003 Joules/kg/year Location - Land or Sea

Extremophiles are organisms adapted to living in extreme environments.

Most Extremophiles are bacteria. Some are eukaryotes and simple animals…. tube worms Were the first forms of life on Earth.

High temperatures are bad for most organisms Heat breaks down chlorophyll, stopping photosynthesis. Heat decreases the amounts of CO2 and O2 in water. Heat breaks down proteins, causing them to stop working.

Thermophiles are organisms that thrive at high temperatures (>110°F) Found in hot springs and deep-sea hydrothermal vents. Have unique proteins & enzymes that work at high temperatures. Most are Chemoautotrophs Get their energy from hydrogen sulfide or methane

Cold temperatures are bad for most organisms Freezing dehydrates cells Cold slows the movement of nutrients & wastes Cold proteins and enzymes get stiff, inhibiting their function Frozen water can form needles-like crystals which puncture cell membranes

Psychrophiles are organisms that thrive at low temperatures (<15°C) Found in glaciers, arctic ice, snow, and soil deep in the oceans. Have flexible enzymes and proteins that act like antifreeze. Some are eukaryotes that live by photosynthesis… snow algae. The methane ice worm , found in Antartic ice cores, is a psychrophile that can survive temperatures from 0 to 5˚C. 

High salinity (too much salt) is bad for most organisms. High salt dries out cells by drawing out water. High salinity promotes proteins to clump together, disrupting function. High Salinity limits the availability of oxygen.

Halophiles are organisms that thrive in high concentrations of salt Live in water with 10x the salinity of the oceans Dead Sea & Great Salt Lake. Extra ions reduce water movement out of the cell, stops drying out.

Halophiles have turned the land that surrounds the Great Salt Lake in Utah a reddish color. This happens to the land after flood waters spread onto the land.

Salt Deposits on the Salt Sea

The Acidity of solutions is measured by its pH. Abnormally High or Low pH solutions can be bad for most organisms. The Acidity of solutions is measured by its pH. High and low acidity can destroys proteins and DNA and inhibit their function.

Acidophiles are organisms that thrive in highly acidic environments Ferroplasma acidarmanus can grow at 0 Ph! It can be found in acid mine drainage. Survive in pH 0 (battery acid) Some have an ability to neutralize their cellular interiors Other acidophiles have evolved acid-stable proteins.

Acidophiles found in a treatment plant in Wales Acidophiles - Organisms that thrive in extremely acidic habitats.  Example: Found in Lechuguilla Cave, Carlsbad, New Mexico, where the pH is 0.0…..about as acidic as battery acid! Acidophiles found in a treatment plant in Wales

Radiation is hazardous to DNA DNA is susceptible to radiation damage: Minor Damage to DNA - limits self-repair Lethal Damage to DNA - results in cell death Non-Lethal Damage to DNA - leads to mutations Radiation Dose = Energy absorbed per kg 10 Joules/kg is lethal to humans 60 Joules/kg kills E. coli bacteria

Radioresistant organisms can survive high doses of radiation Deinococcus radiodurans can survive doses of 5000 Joules/kg Can absorb up to 15,000 Joules/kg with 37% viability Has very efficient DNA repair and carries 4 to 10 copies of its genome Deinococcus radiodurans thrives in the cooling ponds of nuclear reactors amid radioactivity levels lethal to mammals.

Endoliths are organisms that live inside rocks & between mineral grains Found as deep as 2 miles below the surface. Most are chemoautotrophs Reproduce maybe once per century….some colonies live for thousands of years? These Brown Spherical Structures are Endoliths embedded in Quartz

Xerophiles are organisms that grow and reproduce in low water environments. They use endospores, which are dehydrated cells surrounded by a thick protective cell wall, or enter a anhydrobiosis state (no metabolic activity and little intracellular water). Even after 30 millions years, some bacterial spores have been revived.

No rainfall recorded in some regions for the past 400 years! The Atacama Desert of northern Chile is the driest non-arctic place on Earth. Virtually sterile desert 100 times more dry than California’s Death Valley. No rainfall recorded in some regions for the past 400 years!

Results of a 2003 study for life in the Atacama Desert…. No bacteria were found down to 4 inches…. A later study found viable bacteria at depth of 1 foot! It Turns out that Life can exist even in the driest environments as long as there is at least a little liquid water. NASA rover, designed to search for life in the Atacama Desert.

The record holder for reviving dormant bacteria is Strain 2-9-3, found in sea salt, which was revived after 250 million years of dormancy.   Tardigrades can withstand the highest variety of extreme conditions and are capable of entering a low hydration state called tun in which they use .01%  metabolic activity. They can survive a decade without water in the tun state! These organisms look like bears, and inhabit almost every environment on Earth.  Tardigrades are about 0.1 - 0.5 mm

Extremophiles were the first life-forms on Earth. Studying the extremes life forms on Earth can help us in our search for life elsewhere in the Universe. What We’ve Learned The discovery of the existence of extremophiles greatly extends our understanding of the range of possible environments for life. Extremophiles were the first life-forms on Earth. No organisms are known that can survive without liquid water.

Could Extremophiles survive elsewhere in our Solar System?

Mars Mars is one of the first planets most people think of when searching for life outside of Earth. It is cold and dry but with the possibility of liquid water subsurface, organisms such as Tardigrades or Radioresistants could live there. Tardigrades only requires basalt + water and a radioresistant could survive the radiation, dryness and low atmospheric pressure. 

Jupiter’s Moons     Moons such as Europa, Ganymede and Callisto are very promising because they are believed to have oceans below there icy surfaces. Thermophiles could survive, endoliths if there are rock and water combinations, or even psychrophiles on the icy surface of the moons.

Saturn’s Titan The Cassini-Huygens mission surveyed Titan and found similar hydrocarbon compounds in its thick atmosphere.

Especially promising is Saturn’s moon Enceladus Especially promising is Saturn’s moon Enceladus. Pictures taken by the Cassini-Huygens spacecraft show liquid water Geysers. Not only is there water, but carbon and energy are present… the perfect ingredients for life. Liquid Water Geysers

Venus The Clouds in Venus' stratosphere are perfect conditions for acidophiles. The clouds are cooler than the 900˚F surface and there are acid drops in the clouds where acidophiles could survive.

Comets Comets could host organisms such as psychrophiles. These organisms could have a dormancy periods and only reproduce when they are in a habitable zone.