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Extremophiles and the Physical Limits of Life on Earth …And Mars

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Extremophiles and the Physical Limits of Life on Earth …And Mars Extremophiles: defining the envelope for the search for life in the universe Lynn J. Rothschild NASA/Ames Research Center & Stanford University Moffett Field, CA 94035 USA [email protected] Overview · What is an extremophile? · Why do (and did) we study them? · Environmental extremes · How do they do it? · Examples of extreme ecosystems · Space: new categories of extreme environments What is an “extremophil e”? ªextremusº, the superlative of exter, being on the outside plus ªphilosº, love equals Extremophile Coined by Bob MacElroy, NASA Ames Research Center. Macelroy (1974) Some comments on the evolution of extremophiles. Biosystems 6:74-75. Philosophical issues · Physical, chemical, biological(?) extremes? · What is “extreme”? Simply in the eye of the beholder? Evolutionary definition? Objective definition? Caveat: it is important to talk about extremes for certain organisms - e.g., people · Must extremophiles love extreme conditions? · Must extremophile apply to all life stages? At all times? Deinococcus and frogs. Environmenta l extremes Categories of extremophiles Environment Type Definition Examples Temperature Hyperthermophil growth >80°C Pyrolobus fumarii -113°, strain e 121°? Growth 60-80°C Thermophile Synechococcus lividis Growth 15-60°C Mesophile humans Growth <15°C Radiation Psychrophile Psychrobacter, insects D. radiodurans Pressure Weight loving Barophile Pressure loving Piezophile Shewanella viable at 1600 MPa Desiccation Cryptobiotic; Salinity Xerophile anhydrobiotic Haloarcula, Dunaliella pH Halophile Salt loving (2-5 M NaCl) Spirulina, Bacillus firmus Alkaliophile pH >9 OF4 (10.5); 12.8?? Oxygen tension Acidophile Low pH loving Cyanidium, Ferroplasma Anaerobe Cannot tolerate O2 Methanococcus jannaschii Miroaerophil Clostridium Chemical extremes Aerophile Homo sapiens Cyanidium caldarium Vacuum high CO2, arsenic, Electricity mercury Tardigrades electric eels Which taxa contain extremophiles ? Taxonomic Distribution of Extremophiles …but these are just a few examples Courtesy of Pace lab, 2004 Why study extremop hiles? Why study extremophiles? · Food preservation. · Basic research; model organisms for basic research · Biological warfare. · Biotech potential. · Future use in space. · Biodiversity on Earth. Archaea. Origin of life? · Mechanisms of survival: divergence or convergence? Apparent convergence by LGT? · Limits for life in the universe. Life elsewhere Richard Proctor. 1870. Other Worlds Than Ours possibly first to connect study of life in extreme environments and life on other planets. “If we range over the earth, from the arctic regions to the torrid zone, we find that none of the peculiarities which mark the several regions of our globe suffice to banish life from its surface.” (ch. 1) NASA Ames and the history of extremophile research · Ken Souza: We were working with ”extremophiles" well before the term became popular. In the 60's and earlier, people worked with halo, thermo, psychro, alkalo and acido -- philes. Ames dedicated a branch of about 25 civil servant researchers and technicians to biological adaptation (which utilized "extremophiles" to identify and understand the mechanisms life used to survive and reproduce in such harsh environments.) In the early 60's Young and his staff created a ”Mars simulator" and were looking at psychrophiles in freeze/thaw cycles trying to select those most suited to survive putative martian conditions. I spent some years on thermophiles as did Macelroy as potential models of venution life. I also did some work with alkalophiles as potential models of jovian life (putative aerosol water layer). Hochstein, lanyi and others worked with halophiles as putative models for martian life. · Don Devincinzi: I suspect that he (Dick Young) and Chuck Klein started NASA's work on extreme environments at Ames in the mid-60s. · Sherwood Chang: Organisms that survived or thrived under ammoniated conditions were also of interest (remember the so-called primitive Earth's ammonia, methane atmosphere of Urey and Miller), particularly a rather strange bug that I recall was called "kakabeckia" or some such thing. · Bonnie Dalton: “At that time, (1963) we were all looking toward a Mars lander and the need to understand life (if it was there). Of course any life form would have to be of a nature adaptable to very extreme organisms. Our extremeophiles were the halophilic bacteria living in the SF bay.” · “Ames was the Center for this work and thus grew the concept of Astrobiology.” Examples of extreme parameter s Temperature: what difference does it make? . Solubility of gasses goes down as temperature goes up (impetus for colonization of the land?). Organisms have upper temperature limits. Chlorophyll, proteins and nucleic acids denature at high temperatures. Enzymes have optimal temperatures for activity; slow down at low temperature . Low temperature water freezes. Breaks membranes, increases solute concentration, etc. Temperature limits for life* 150 sulfur dependant archaea methane-producing archaea 100 Pompei worm heterotrophic 70?Pompei worm bacteria cyanobacteri anoxygenic s a photosynthetic 50 e fung l fung alga i protozo h i e p mosses a o s e m vascular plants insects ostrocods 0 fish fung alga protozo bacteri archaea i e a a Himalayan midge and….? -50 * However many organisms, including seeds and spores, can survive at much lower and higher temperatures. SynechococcusSynechococcus C ° 5 high temperature 6 ~ , Life at s u x e C f ° o 5 r 7 lo h C Thermocrinis ruber ~83°C Source, > 95°C Park, 4 July 1999 Octopus Spring, Yellowstone National History of high temperature extremophile research - Tom Brock, Karl Stetter · Brock’s first visit to YNP was July 1964, and was surprised by organisms in run-off channels. Stopped again to sample later in the summer. Then started to do work in YNP to get field experience before field trip to Iceland. Studies in photosynthesis, chlorophyll, RNA, DNA and protein. · 1965 tried to culture at high temperature using spring water as culture medium and springs as incubators (didn’t work.) Noticed pink, gelatinous mat at Pool A (Octopus Spring.) High temp at the time was considered 60°C. · Fall 1965 wrote NSF proposal, which was funded, and serious YNP work started 1966. Hudson Freeze cultured YT-1, later known Thermus aQuaticus. · Near end of summer of 1967, starting using immersion slide techniQue. String in source of Octopus - first evidence for life growing in source. Later than summer showed life in boiling water. · Stetter’s original interest was looking at polymerases in Woese’s newly-proposed Archaea. History of Deep Sea Extremophile Research - Alvin In 1977, Alvin traveled through the Panama Canal for the first time. Geology work in the Galapagos Rift was completed during February and March. The major discovery of an abundance of exotic animal life on and in the immediate proximity of warm water vents prompted theories about the generation of life. Since no light can penetrate through the deep waters, scientists concluded that the animal chemistry here is based on chemosynthesis, not photosynthesis. Since then, Alvin has located more than 24 hydrothermal sites in the Atlantic and Pacific Oceans. It also has allowed researchers to find and record about 300 new species of animals, including bacteria, foot-long clams and mussels, tiny shrimp, arthropods, and red-tipped tube worms that can grow up to 10 ft long in some vents. History of psychrophile research · Food preservation: As old a method as drying. Many Arctic communities preserved food in holes in the ice. · Snow algae - Ferdinand Cohn? · Early work on psychrophiles from the marine environment (Certes in the 1880’s and Conn in the early 20th century). ZoBell and his students particularly Dick Morita studied these organisms and were the first to get really deep-sea samples from the 1957 Galathea expeditions to ocean trenches. They were the first to study psychrophiles and barophiles. · Antarctic research, especially in prep for Mars Lake Hoare Dry Valleys Antarctica under Lake Hoare preparing to dive under Lake Hoare mat layers lift-off microbial mat heather pH limits for life sedges Natronobacterium sphagnum Bacillus firmus algae ephydrid flies OF4 Spirulin fung a i protist Archae Synechococc s a us rotifer Sulfolobus carp s haloarchea 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH Zygogonium sp. Zygogonium is a genus of filamentous green algae. This species is acidophilic. What has driven pH work? · Food preservation. · Biotech. Recent example. Kenya Wildlife Service (KWS) planned to launch a multi-million dollar legal claim against Genencor and Procter & Gamble, alleging that a microbial cellulase enzyme illegally obtained from a soda lake in the country was used as an ingredient in the latter company's Tide laundry detergent. Kenyan dispute illuminates bioprospecting difficulties. Nature Biotechnology 2004. http://www.nature.com/news/2004/041108/pf/nbt1104-1337_pf.html · Biochemistry. · Life on Venus. Sechbach and others in 1960s. History of Halophile Research · Noted red waters in biblical times, as did Darwin in South America. But halophiles first noted as cause because of food preservation issues. · Preparation for Viking. · Evaporites - endoevaporites; panspermia and Mars. · Biotechnology. Salinity · Halophiles: 2-5 M salt · Include Archaea and a eukaryote. · Dunaliella salina is used in biotech industry. Produces glycerol and - carotene. · The bacterial halophiles have been fown in space. · Have internal osmotica (e.g., K+, glycine betaine). Desiccation - food preservation
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