PTYS 214 – Spring2011  Homework #7 DUE in class TODAY  Homework #8 available for download on the class website DUE Tuesday, Apr. 5  Class website: /  Useful Reading: class website  “Reading Material” Announcements

Quiz #6  Total Students: 23  Class Average: 2.6  Low: 0.5  High: 4 Quizzes are worth 20% of the grade

Extreme Environments Physical extremes: - Temperature - Pressure - Radiation Geochemical extremes: - pH (acidity levels) - Salinity - Desiccation - Oxygen species - Redox potential For any particular property (T, pH, salinity) extreme values are values far from the typical range for human life

Extremophiles Organisms (mostly microbes) that thrive in (and sometime require) extreme conditions The earliest living organisms on Earth were extremophiles Early-Earth environment: – Atmosphere without oxygen: no UV protection – Oceans were hot and probably acidic (volcanism)

Importance of Temperature  Organisms have upper temperature limits - chlorophyll, proteins and nucleic acid denature at high temperatures  Enzymes have optimal temperatures for activity - they slow down at low temperatures  Solubility of gases goes down as temperature goes up  At low temperature water freezes; crystals then break up membranes etc. (but the expansion of water to ice means layers of ice ‘insulate’ water below… for most liquids lakes would freeze from bottom up)

Thermophiles High Temperature Lovers  Reproduce and grow readily in temperatures higher than 45°C (geothermal sites)  Hyperthermophilic  Optimum growth at >80°C (hydrothermal vents) Current upper limit for active growth is 121°C - Pyrolobus fumarii - 1 μm

Example: Octopus Spring, Yellowstone Nat. Park (pH: ) Rotschild & Mancinelli (2001) Life in extreme environments. Nature 409, 1092 Synechococcus Thermocrinis ruber Chloroflexus and others

Planet Earth Video

Psychrophiles or Cryophiles Low Temperature Lovers  Obligatory psycrophilic (“cold loving”)  No growth at >15°C ( polar sediments, sea ice )  Psychrophilic  Optimum growth at <20°C ( polar sediments, sea ice )  Current lower limit for active growth is -20°C (water with high salt content can be liquid even at -30°C) Grylloblatids, or ice bugs, have body fluids that act as antifreeze

Snow algae (red snow or watermelon snow) are cold-tolerant algae and cyanobacteria that grow on snow and ice during alpine and polar summers

Liquid water + salts

High Pressure  High pressure can make the cell membranes relatively impermeable for nutrients  Piezophilic (or barophilic)  Optimum growth at >>1 atm some growth at 1 atm  Obligatory piezophilic  Cannot survive at low pressures Current upper limit is >1000 atm - Halomonas salaria – an obligatory piezophile (at the bottom of the Marianas Trench, 10,898 m, pressure is ~800 atm)

High-Low Acidity (pH)  pH = -log 10 [H + ] Amount of H +, it measures the acidity of a solution  Within the cell pH levels must be neutral (proteins denature at very low pH)  Acidophile  Optimal growth at pH <  Alkaliphile  Optimal growth at pH >

pH limits  Current limits: pH ~0 Ferroplasma acidarnamus (acid mine drainage, Iron Mountain, CA) pH = 13 Plectonema (soda lakes)

Tinto river (Andalusia, Spain) With a pH of about 2 (causing Fe to be soluble in water), it has gained scientific interest due to the presence of extremophile aerobic bacteria that dwell in the water

Salinity  Prevents protein aggregation: proteins are less soluble at high salt concentrations  Halophilic  Optimum growth at seawater salinity (~3%)  Extremely halophilic  Optimum growth in solutions with > 10-15% salt Dunaliella salina a halophilic pink micro-algae especially found in sea salt fields, can survive in saturated salt water

Water availability  Extreme desiccation can cause irreversible phase changes to lipids, proteins and nucleic acids  Xerophiles  grow in environments with low water availability (low “water activity” a w <0.8) −a w (distilled water) = 1 −a w (saturated NaCl) = 0.75 −a w (honey or indoor air) =  Mold and yeast can survive at a w = 0.6

Tardigrades – “water bears”  No larger than about 1 mm, they have short, plump bodies  In anhydrobiosis (their body desiccates and waits for moisture to return) they can survive: °C (0.05K) for 20 Hours -200°C for 20 Months +120°C (above boiling) Pressures of 1,000 atm Pure vacuum Live over 125 years

Endoliths  Anaerobic organisms that live in the pores between mineral grains of a rock and can survive by feeding on Fe, K, or S (they can “eat” rock)  Found in rocks as deep as 3 km, where both temperature and pressure are quite high Bacillus infernus is an endolitic hyperthermophile found up to 3 km beneath the Earth's surface Photo courtesy of US Dept. Energy

Example: Beacon sandstone, McMurdo Dry Valleys, Antarctica Polyextremophiles Organisms that combine several extremophilic features (most extremophiles are really polyextremophiles) Blue bands are layers of cryptoendolithic lichen communities (algae, fungi and bacteria)

One of the most radiation-resistant organisms known, it can survive cold, dehydration, vacuum, and acid Polyextremophiles: Deinococcus Radiodurans (a.k.a.“Conan the bacterium”) Radiation-resistant: it can stand around 1,000 time radiation amounts that would kill humans!  It carries between 4 and 10 copies of its DNA, making it easy to repair damage from radiation, or dehydration

Arsenic-based Life?

Activity Extreme Environments and the Life that Lives there

Bacteria A  Environment X: too cold + no chemical energy + no org. C Environment Y: too hot + no organic C + no salinity (survives even if light decreased nearly to zero) Bacteria B  Environment Y: no oxygen + too hot + low salinity Environment Z: no oxygen + no inorganic C (it appears as it needs light to survive) Bacteria C  Environment X: no chemical energy + too cold + high salin. Environment Z: no inorganic C + high salinity (survives even if light decreased nearly to zero) Environment Z Environment X Environment Y Activity: Extremophiles

Looking for “strange life” on Earth…  Any new hydrothermal vent contain new life forms  deep sub-seafloor biosphere is the least explored habitat on Earth, yet it may make up 1/10 to 1/3 of Earth’s living biomass!  Lots of new life forms await our discovery… …may teach us to look for “strange life” beyond Earth!

Mars may have regions in its deep subsurface permafrost that could harbor endolith communities On Europa, the subsurface water ocean may harbor life, especially at the hypothesized hydrothermal vents at the ocean floor. Venus ’ stable cloud layers, 50 km above the surface, have hospitable climates and chemical disequilibrium, fueling speculations that microbes could live there On Titan, data from Cassini/Huygens suggest a near-surface chemistry consistent with the hypothesis that organisms may be consuming hydrogen, acetylene and ethane, to produce methane (but this is not proof) Earth’s ‘Extreme’ is ‘Normal’ Somewhere Else…