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Life in Extreme Environments

Life in Extreme Environments. Extremophiles on Earth. Reading Assignment. “ Energy and Life in Unique Environments on Earth ” From: The Search for Life on Other Planets by Bruce Jakosky, 1998, pp. 72–92 (at back of course packet) SETI Module ( “ Topics”  “Search for Life”)

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Life in Extreme Environments

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  1. Life in Extreme Environments Extremophiles on Earth

  2. Reading Assignment • “Energy and Life in Unique Environments on Earth”From: The Search for Life on Other Planets by Bruce Jakosky, 1998, pp. 72–92 (at back of course packet) • SETI Module • ( “Topics”  “Search for Life”) • Scientific American • “Extremophiles” • April 1997 (online via www.sciam.com)

  3. Some extreme environments for Homo sapiens

  4. Astrobiology • Study of the origin, evolution, distribution, and destiny of life in the universe • Extremophiles on Earth • Fragility & robustness of life on Earth • Extinctions (& evolution) • Discoveries of planets outside solar system • Water on Mars & Jovian moon Europa? • Comet and asteroid impacts (Earth, Mars, …)

  5. Cosmic Calendar • From Dragons of Eden by Carl Sagan • http://home.pacific.net.hk/~paulchui/cosmic.html

  6. Extreme Environments • Extremophiles • pH: acidophiles & alkalophiles • T: thermophiles & psychrophiles • Salt: halophiles • Dry: xerophiles • etc.

  7. Yellowstone hot springs Full of hyperthermophiles

  8. Discovered in Yellowstone hot springs in 1965 prefers 70–75°C Biotech application polymerase chain reaction (PCR) Taq polymerase Thermus aquaticus

  9. Antarctic dry valleys (deserts)

  10. sulfide chimneys Hydrothermal vents “black smokers” Alvin

  11. Tubeworms Clams

  12. Shrimp in hydrothermal vents These shrimp have sensitive “vision” (with “eyes” on their backs!), even though live in utter darkness. Why?!

  13. Deinococcus radiodurans • Isolated from cans of meat exposed to sterilizing doses of radiation • Ancient (older lineage than other eubacteria) • Can survive 5 Mrad of gamma radiation! (3000 human lethal dose) • exceptional DNA repair mechanisms • Application: biodegradationof toxic solvents in radioactive waste sites (toluene and chlorobenzene) • From Mars?? (after asteroid impact)

  14. Domain Archaea • Methanogens • anaerobic methane producers • Extreme Halophiles • salt-dependent organisms • Hyperthermophiles • heat-dependent organisms • Thermoplasma • heat and acid-dependent organisms lacking cell walls

  15. Halobacterium salinarium • Extreme halophile (salt loving) • Bacteriorhodopsin* • Light pumps H+ out • Leads to ATP production* • Halorhodopsin • Light pumps Cl- in • Sensory rhodopsins • Phototaxis (swimming) *special type of photosynthesis w/o chlorophyll

  16. Traditional Five-Kingdom Scheme

  17. Reformulated “Tree of Life” 3 domains (or superkingdoms) based on DNA sequence comparisons for (16S)rRNA’s (see Jakosky reading, pp. 87–91) ribosomal

  18. Phylogeny

  19. Summary • Diverse organisms thrive in ecological niches that we consider extreme (if not inhabitable). • Hyperthermophiles may well represent early life on Earth when conditions were much “harsher” than now. • Higher organisms like H. sapiens, which arose only very recently in geological time, may be thought of as representing truly odd forms of life on this planet; the “extremophiles” were here first and may be thought of as the norm for life on Earth.

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