Phys 214. Planets and Life

1. Phys 214. Planets and Life Dr. Cristina Buzea Department of Physics Room 259 E-mail: cristi@physics.queensu.ca (Please use PHYS214 in e-mail subject) Lecture 19. Life at the extremes. Part II February 27th, 2008

2. Contents • Life at the extremes • Low-temperatures • High-salinity

3. Low Temperature Temperature limits for life. The highest and lowest temperature for each major taxon is given. Archaea are in red, bacteria in blue, algae in light green, fungi in brown, protozoa in yellow, plants in dark green and animals in purple. (NATURE | VOL 409 | 22 FEBRUARY 2001) Ostrocods = small crustaceans (1 mm size), protected by a bivalve-like "shell". Protozoa = one-celled eukaryotes. Algae = diverse group of simple plant-like organisms, unicellular to multicellular. The most complex -seaweeds; they lack the distinct organs of higher plants such as leaves and vascular tissue. Complex organisms (Eukarya) occupy a more restrictive thermal range than Bacteria and Archaea

4. Low temperature - Psychrophiles Subglacial stream - Glacier du Mont Mine, Swiss Alps. Psychrophiles - extremophiles capable of growth and reproduction at or below 15oC. Environments ubiquitous on Earth - alpine and arctic soils (permafrost), high-latitude and deep ocean waters, arctic ice, glaciers, snowfields, & refrigerated appliances. 1) Obligate psychrophiles - have optimum growth temperature of 15°C or lower and cannot grow in a climate hotter than 20°C. (Antarctica or at the freezing bottom of the ocean floor) 2) Facultative psychrophiles - can grow at 0°C up to ~ 40°C, and exist in much larger numbers than obligate psychrophiles. Many phychrophiles are polyextremophiles: The ones living in deep ocean waters -> extremely high pressures Organisms in sea ice are exposed to high salt concentrations. On snow, glaciers, polar surface organisms are exposed to strong UV radiation. Organisms found in rocks in Antarctic dry deserts - low water and nutrients.

5. Psychrophiles Universal phylogenetic tree features hyperthermophilic (grow >90o), and cold adapted species – phychrophilic (blue lines), or psychrotolerant (violet lines) of Bacteria and Archaea. Permanently cold habitats would favour the evolution of obligate phychrophiles. Psychrophiles are well represented by all three domains of life, Bacteria, Archaea, & Eukarya. Obligate psychrophiles have evolved only among the Bacteria. Many Eukaryotes: Diatoms, Lichens, Nematodes (Panagrolaimus davidi), Antifreeze Fish (Paraliparis Devriesi), Tardigrades, Himalayan midge.

6. Psychrophiles South Pole bacteria. NSF • (Brine is water saturated or nearly saturated with salt) (Planets and life, Sullivan and Baross)

7. Psychrophiles At very low temperatures the water becomes ice. However, small amounts of liquid water are available for life in different types of ice formations, especially at brine inclusions. Water can remain liquid at temperatures lower than -30oC in the presence of salts and other solutes. Many species of snow algae were observed on Alaskan glaciers (green algae and cyanobacteria). Some of them produce brilliant colored spores. They alter the albedo of the snow and induce snowmrlt, incresing the availability of liquid water. Some organisms produce extra-cellular enzymes that lead to pitting of ice. Microorganisms are abundant in frozen environments. Possibility of life on Mars, and other icy bodies? (brine = water saturated or nearly saturated with salt) (albedo = the extent to which it diffusely reflects light from the sun) Chlamydomonas nivalis This is most well-known snow alga. Bloom of this alga causes visible red snow (watermelon snow). This species is common in North America, Japan, Arctic, Patagonia. The algae prefer snow surface rather than ice on glaciers. www-es.s.chiba-u.ac.jp/.../snowalgae_ak.html

8. Low temperature What happens at low temperature to most organisms? Microorganisms face a number of biochemical challenges at low temperatures: A) Lower rate of biochemical reactions - increse in viscosity and decline in mobility (for every 10oC drop in temperature, there is a reduction by a factor of ~2 in the rate of most biochemical reactions) B) reduction in membrane lipid fluidity C) decreased protein flexibility At even lower temperatures, such as near-freezing or even freezing temperatures - all macromolecular biosynthesis (DNA, RNA, proteins, and cell wall) presumably stops. Freezing of water within a cell is lethal. Exception - nematode Panagrolaimus davidi, which can withstand freezing of all of its body water.

9. Subjecting cells to freezing Cells cooled too slowly -> the outside environment freezes first and extracelluar ice forms -> creates a chemical potential difference across the membrane of cells -> the water flows outside the cell -> cell shrinking and dehydration -> irreveresible damage Cells cooled too quickly -> retains water within the cell -> the water expands when frozen -> ice crystals physically destroy the cell “intracellular ice injury”. http://www.scq.ubc.ca/a-cold-greeting-an-introduction-to-cryobiology/

10. Psychrophiles adaptations Antifreeze Fish (Paraliparis Devriesi) Adaptation: strategies A. To compensate for the increase in viscosity and decreased mobility A1. Freezing avoidance - salts and solutes, plus antifreeze cryoprotectant proteins (glycoproteins) lower the freezing point by 10 to 20oC. Cryoprotectant proteins are water miscible liquids, they protect the cell from freezing by reducing the severity of dehydration effects and preventing the formation of ice crystals within body. Antarctic fish are able to survive with very small ice crystals present in their body fluids. A2. Freezing tolerance. Allow the external environment to freeze (extracellular water)-> the change in thermal conductivity insulates the cell against internal freezing (small number of frogs, turtles, and snake) B. To compensate for the decreased fluidity in cell membrane - the ratio of the unsaturated to saturated hydrocarbons must be increased (polyunsaturated fatty acids in cell membrane) C. To compensate for decreased protein flexibility - changes in the structure of a cell's proteins -use enzymes with folds and shapes that promote less rigidity. Increased expression of heat shock proteins when the temperature is lowered. To form spores or cysts and try to outlast the cold period (for geologic lengths of time and become viable again!) Some bacteria survived freezing and thawing without spore formation.

11. Heat shock proteins Sudden decrease in temperature can initiate specific alteration in gene expression - synthesis of heat-shock proteins Heat shock proteins = molecular chaperones for proteins - play an important role in assisting protein folding and the establishment of proper protein conformation. These so-called “heat shock proteins” are not simply heat proteins. They should more appropriately be called “temperature and stress proteins”. Production of high levels of heat shock proteins can be triggered by exposure to different environmental stresses: heat, cold, inflammation, toxins (metals), ultraviolet light, starvation, hypoxia (oxygen deprivation), water deprivation. The structure of the E. coli GroEL heat shock protein. The apical region is capable of polypeptide binding. The lower region, (circled, bottom) is concerned with ATP binding. http://cryo.naro.affrc.go.jp/index_e/noukenyouranE0721.htm National Agriculture and Food Research Organization

12. NASA astrobiologist revives 32,000 year old bacteria NASA astrobiologist takes ice samples from the permafrost in Alaska. The samples, dating back some 32,000 years, contained living organisms. NASA/R. Hoover Carnobacterium pleistocenium - alive after been thawed from ice dating back some 32,000 years. Living bacteria are stained green. Image credit: University of Alabama at Birmingham Bacteria revived after being frozen 32,000 years ago! Carnobacterium pleistocenium - found in an ice samples from the permafrost in Alaska (A layer of soil beneath the earth's surface that remains frozen throughout the year) dating back some 32,000 years. Bacteria had frozen near the end of the Pleistocene Age, which extended from about 1.8 million years ago to just 11,000 years ago--and earned the new bacterium its name. New species of microbe found alive in ancient ice - bacteria started swimming around on the microscope slide. Conclusion: microorganisms can be preserved in ice for geological periods of time! SEM of carnobacterium pleistocenium, International Journal of Systematic and Evolutionary Microbiology (2005), 55, 473

13. PsychrophilesEukaryotes - Himalayan midge

14. Psychrophiles Eukaryotes - Antarctic nematode The Antarctic nematode Panagrolaimus davidi is the only animal known to survive extensive intracellular ice formation. (Nematode = unsegmented worm-like organisms) If freezing rate is slow, the nematodes appear not to freeze. Instead they dehydrate due to the vapour pressure difference between the supercooled body fluids within the nematodes and that of the surrounding ice—a process known as cryoprotective dehydration. Nematode Panagrolaimus davidi (A) Frozen at approximately — 20°C. Bright areas in the nematode and the background are due to ice crystals. (C) Just before the disappearance of the last ice crystals during melting.

15. Low temperature ecosystems Diversity of low-temperature ecosystems! From shrimp to whales! Deep under the Antarctic ice live lots of species of fish, sea stars, jellyfish, shrimp, as well as marine mammals and penguins, to name a few. Photos Credit: Henry Kaiser, NSF

16. Psychrophiles - Polyextremophiles - Diatoms Surirella diatom -in alkaline and hypersaline Mono Lake. The large milky turquoise patch visible below the southern coast of Newfoundland, is a bloom of phytoplankton. Diatoms - major group of unicellular eukaryotic algae; one of the most common types of phytoplankton (microscopic plants found in bodies of water). • encased within a cell wall made of silica (hydrated silicon dioxide). • wide diversity in form, usually consist of two asymmetrical sides with a split between them, hence the group name. Environment - wide variety of extreme environments, including ancient Antarctic Ice, high salt concentrations.

17. Psychrophiles - Polyextremophiles - Lichens Lichens - symbiotic associations of a fungus with a photosynthetic partner that can produce food for the lichen from sunlight (green alga or cyanobacterium). • are often the sole vegetation in some extreme environments - high mountain and at high latitudes; deserts, frozen soil of the arctic regions. European Space Agencyexperiment shows that lichens can endure extended exposure to space: lichens exposed for 14 days to vacuum, wide fluctuations of temperature, the complete spectrum of solar UV light and bombarded with cosmic radiation. • full rate of survival and an unchanged ability for photosynthesis! • Able to recover in full their metabolic activity within 24 hours after extreme dehydration induced by high vacuum. (Astrobiology. 2007 Jun;7(3):443-54.) • Experiment extremely important for the possibility of transfer of life between planets (via meteorites)! Courtesy ESA. http://www.esa.int/esaCP/SEMUJM638FE_index_0.html

18. Psychrophiles - Polyextremophile - Tardigrades Tardigrades (water bears) = small, segmented animals; length 0.1-1.5mm. Environment: from Himalayas (above 6,000 m), to the deep sea (below 4,000 m) and from the polar regions to the equator; in lichens, beaches, soil and marine or freshwater sediments (up to 25,000 animals per litre). Tardigrades have been known to survive the following extremes: 1)Temperature - a few minutes at 151°C; days at minus -200°C. 2)Radiation 100 times higher than lethal dose for humans 3)Pressure very low (vacuum); very high pressures 6,000 atm 4) Dehydration Adaptation:capable of entering a latent state - cryptobiosis - when environmental conditions are unfavorable. Cryptobiosis = the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill (a unique biological state between life and death - potentially reversible death). - poorly understood (read more in Y. Neuman / Progress in Biophysics and Molecular Biology 92 (2006) 258–267)

19. High Salinity - Halophiles Salt flats at Lake Magadi, Kenya. The flats are red due to the proliferation of halobacteria Owens Lake. The pink coloration is caused by halobacteria living in a thin layer of brine on the surface of the lake bed. An aerial view shows the pink water of Great Salt Lake brushing up against the Eco-sculpture "Spiral Jetty" on a salt-crust shore. Image credit: Bonnie Baxter. Halophiles -salt-lovers Halotolerant = are not dependent upon salts in growth media but can tolerate up to 15% salinity. Extreme halophiles (often known as halobacteria) - unable to survive outside their high-salt native environment; primary inhabitants of salt lakes, where they tint the water and sediments with bright colors. Domains: Archaea, Bacteria, smaller number of Eukarya (yeasts, algae and fungi); Halobacteriacea, Dunaliella salina Environment: places where exposure to intense solar radiation leads to evaporation and concentration of NaCl to near- or even super-saturation; hypersaline bodies of water that exceed the 3.5 % salt of Earth’s oceans, Great Salt Lake in Utah, The Dead Sea.

20. High Salinity - halophiles What happens at high salinity to most organisms? The greater the difference in salt concentration between in and outside the cell - the greater the osmotic pressure (hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute). If we drink salty water we desiccate the cells -> enzymes and DNA denature or break! Plants: trigger ionic imbalances -> damage to sensitive organelles such as chloroplast. Animals: a high salt concentration within the cells -> water loss from cells -> brain cells shrinkage -> altered mental status, seizures, coma, death. (Natural salts were used to remove moisture from the body during mummification). Adaptation: Two strategies to cope with osmotic stress: 1) Maintain high intracellular salt concentration. Requires extensive adaptation of the intercellular machinery (few specialized organisms). 2) Cells maintain low salt concentration in the cytoplasm, the osmotic pressure being balanced by: - producing or taking from the environment, and accumulating in the cytoplasm organic molecules (glycerol, amino acids, sugars). - selective influx of K+ ions into the cytoplasm.

21. High Salinity - Halophiles Cross section of the filamentous cyanobacterium Microleus embedded in a matrix of a microbial mat. Solar Lake, a hypersaline pond in Egypt. Cyanobacteria, the first ever oxygenic photosynthesizers, are said to be the source of chloroplasts in eukaryotes. They are commonly associated with extreme environments Cyanobacteria - (sometimes called blue-green algae) group of photosynthetic and aquatic bacteria (not Eukarya!) that contain chlorophyll. Very important in Earth’s ecological change - the source of the oxygen atmosphere during the Archaean and Proterozoic Eras; the origin of plants: the chloroplast in plants is assumed to be coming from symbiosis with a cyanobacterium. Cyanobacteria can survive in small pockets of water within deposits of salt after water evaporation. These type of deposits found on Mars. Jupiter's moon Callisto may have an underground saline ocean, as well as on the neighboring moon, Europa.

22. High Salinity - Halophiles Dunaliella - extremely halophilic green algae; main food source for brine shrimp. Aphanothece - a blue green alga in hypersaline environments Great Salt Lake water inoculated on media plates yields colonies boasting colorful carotenoids. Inhabitants of hypersaline lakes experience intense ultraviolet (UV) light. In order to survive UV, halophiles have efficient DNA repair, but they also have mechanisms to prevent damage. Halophilic Archaea have a low number of UV "targets," thymine (one of the four bases in the nucleic acid of DNA), in their genomes. Colorful carotenoids – important class of antioxidants that may provide protection from UV damage -strategy for photoprotection as mutant colorless halophiles are UV sensitive.

23. Longevity of Halophiles? Increasing evidence for the presence of viable microorganisms in geological formations that are millions of years old. It is not known if ancient salt deposits are • only a storage area for dormant microorganisms, • or they provide a subsurface habitat in which halophilic microorganisms can grow and multiply. The possibility that halophilic microbes could survive in a state of dormancy over geological time periods remains to be proven unequivocally. Long-term dormancy cannot definitely be ruled out -> relevant for possible life on planet Mars, who was hotter and wetter in the past!

24. Next lecture More extremophiles! High sugar concentration High pressure Low pressure Bacteria that had a trip to the Moon Alkaline and acid environments Radiation Subsurface rocks oxygen