Background: Why study life in the cold?
 

Despite the fact that >80% of the biosphere (by volume) is permanently below 5°C and most of the biomass is microbial, very little is known about the biology of microorganisms inhabiting permanently cold environments.   Recent discoveries of microbial life in deep glacier ice and subglacial environments have extended the known boundaries for life into icy realms.  The discovery of active microbial assemblages beneath glaciers and realization that large quantities of liquid water exist beneath polar ice sheets has resulted in a new paradigm in the study of life on Earth.  Considering this, it is vital to understand the biogeochemical contributions and role of permanently cold ecosystems in the biosphere.

The study of ecosystems in the cold deep biosphere also has implications for the natural history and evolution of life on Earth.  Geological evidence indicates that a long period of low latitude pervasive global glaciation occurred during the late Proterozoic, referred to as a “Snowball Earth” .  It is believed that the planet was completely covered in ice for at least 10 million years and liquid water only existed in the ocean under a thick ice cover. If this scenario is accurate, such a long period of global freeze would have had drastic consequences on ecosystems established prior to this event, and glacial and subglacial environments may have provided an important refuge for life during such an extended ice age. 

Microbial life appeared on Earth's surface rapidly after conditions were permissive (at least 3.9 billion years ago), and this coupled with an awareness of the tenacity life implies that geological and physical settings in the universe similar to those on Earth may also harbor life.  Polar ice caps composed of water ice exist on Mars, there is evidence for glaciers at lower latitudes during times of higher obliquity, and the jovian moon Europa is thought to maintain a 50-100 km deep liquid ocean under a 3-4 km ice shell. Thus, the study of cold, dark, subglacial environments on Earth will provide insight as to the likelihood of microbial life surviving and persisting in icy extraterrestrial environments. Furthermore, the challenge of identifying appropriate extraterrestrial sites for exploration and developing technology to sample icy subsurface environs will directly benefit from the experience gained by studying earthly analogs.

Current Research in the Christner Laboratory:

GeomicroBiology of Antarctic Subglacial Environments (GBASE) Beneath the Whillans Ice Stream
The GBASE project is one of three research components of the WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) integrative initiative that is being funded by the Antarctic Integrated System Science Program of NSF's Office of Polar Programs, Antarctic Division. The overarching scientific objective of WISSARD is to assess the role of water beneath a West Antarctic ice stream in interlinked glaciological, geological, microbiological, geochemical, and oceanographic systems. GBASE will examine distinct, but hydrologically related, subglacial environments using a combination of biogeochemical/ genomic measurements to answer key questions directly relevant to metabolic and phylogenetic biodiversity, and the biogeochemical transformation of major nutrients beneath the Whillans Ice Stream. We expect the microbial communities associated with the ice stream to be a metabolically dynamic ecosystem, and specifically ask (1) what is the microbial community structure and (2) what is the metabolic function of the community in situ? Understanding biogeochemical processes involved with elemental transformations on our planet is a central theme in NSF's decadal plan and the use of multidisciplinary tools to study these transformations in polar regions has been recommended by a 2007 NRC report that states "It is time for scientific research on subglacial lakes to begin". GBASE results will be used by investigators of LISSARD and RAGES (the other two components of the WISSARD project) to cast their results in a holistic ecosystem perspective.
Funding: National Science Foundation, Antarctic Integrated System Science

DNA Repair Under Frozen Conditions: Implications for the Longevity of Microorganisms in Terrestrial and Extraterrestrial Ices
Ambient levels of natural ionizing radiation are of little consequence to microorganisms inhabiting most environments on Earth. However, in the absence of metabolic activity over a prolonged timeframe, a dormant microorganism would eventually receive a dosage beyond which effective repair is no longer possible. Microbiological investigations of ancient glacier ice and permafrost have documented viable bacteria in samples hundreds-of-thousands- to millions-of-years old. Recent laboratory studies have demonstrated that microorganisms remain metabolically active in the liquid fraction of ice matrices at temperatures as low as -20oC, supporting the notion that some level of metabolism may occur in permanently frozen environments. The ability of cells to remain metabolic activity (e.g. to conduct DNA repair) in ice would allow viability for extended periods of time, and the longevity of microorganisms under frozen conditions may only be limited by the water activity and availability of energy and nutrient sources. The objectives of the proposed research are to: (1) examine the physiological and biochemical effect of sublethal levels of ionizing radiation on populations of ice-entrapped bacteria; (2) evaluate the ability of microorganisms to repair chromosomal damage sustained from ionizing radiation under frozen conditions; (3) establish the rate of macromolecular synthesis under frozen conditions that is required to effectively repair cellular damage resulting from single- and double-stranded DNA breakage and protein oxidation; and (4) improve predictions for the radiation-dependent limit for microbial longevity in terrestrial and extraterrestrial ices. This study will examine biological repair mechanisms at temperatures germane to those existing in icy extraterrestrial environments (e.g., the polar regions of Mars) and increase scientific knowledge on the metabolic capabilities of bacteria at subzero temperatures.
Funding: National Aeronautics and Space Administration, Astrobiology: Exobiology and Evolutionary Biology

Modes of Adaptation, Resistance, and Survival for Life Inhabiting a Freeze-dried-radiation-bathed Environment (MARSLIFE)
The presence of water on Mars and on a number of planetary moons (e.g., Europa, Enceladus, Ariel, and Triton) suggests that multiple loci within the solar system may plausibly support microbial life. The overarching theme of the project proposed here, MARSLIFE, is that selective pressures in terrestrial extreme environments serve as “training grounds” that enrich for microbial phenotypes that may dominate extraterrestrial habitats on Mars and elsewhere. The MARSLIFE program will: (i) investigate existing and novel microorganisms with tolerances to cold, desiccation, and radiation as models for astrobiology; (ii) use laboratory simulators to assess responses of selected extremophiles to temperature, pressure, and radiation conditions that exist in a range of extraterrestrial environments; (iii) characterize biological resistance mechanisms to freezing, desiccation, and radiation, and (iv) improve technologies for the detection and sampling of microorganisms under conditions similar to the surface of Mars. The expected outcomes include the development of fundamental astrobiological concepts and operational capabilities that would promote the success of future NASA-driven life detection missions, inform policies on planetary protection, and lay the foundation for a new space research enterprise in Louisiana. The institutions, LSU, SU and LaTech, bring together a variety of research and education capabilities and, in conjunction with NASA mentors, the relationships nurtured within MARSLIFE will produce technologically informed, interdisciplinary scientists, foster new technology and educational opportunities, and increase the collaboration between NASA and Louisiana.
Funding: National Aeronautics and Space Administration (Experimental Program to Stimulate Competitive Research; EPSCoR) and the Louisiana Board of Regents

Biogeochemistry and Geomicrobiology of Taylor Glacier Basal Ice
To examine if microorganisms are metabolically active in glacier ice, we are conducting a comprehensive assessment of the biogeochemistry and geomicrobiology of Taylor Glacier (McMurdo Dry Valleys, Antarctica) basal ice via a combination of field measurements and laboratory experiments. A key component of the study is the ability extract parallel large volume samples (~10 kg) for analysis of nutrients, gas composition, d13C-CO2, cell density, metabolic activity, genomic DNA, and nucleotide ratios. Importantly, these large ice samples provide biomass (106-108 total cells) and CO2 in quantities ~100x greater than typically available using ice core materials, permitting experiments that are difficult or unfeasible with ice core archives, such as measuring the isotopic composition of CO2, nucleic acid characterization, and parallel biogeochemical and microbiological analyses.  Using this approach, we are able to connect nutrient availability, geochemical composition, and gas composition with microbial cell density, diversity and metabolic status in the basal ice sequence. Multi-sample analysis of the same ice facies is the best available method to understand the chemical and microbial process linkages in basal ice and the manner by which microbes may modify gas compositions in situ.
Funding: National Science Foundation, Antarctic Organisms and Ecosystems


ICIBASE tunnellers: Top - Timothy Brox, Scott Montross, and Shawn Doyle. Bottom - Pierre Amato and Brent Christner.


B-236 2009-10:  Top - Scott Montross, Brent Christner, Amanda Achberger, and Timothy Brox. Bottom - Lindsay Knippenberg, Shawn Doyle, and Mark Skidmore.

Shawn Doyle's 2009 Antarctic Field Blog

Polar TREC teacher Lindsay Knippenberg

High Altitude BIological Testing of the ATmosphere (HABITAT): Developing a Sampling Platform to Measure the Upper Boundaries of the Biosphere  
We are designing, fabricating, and field testing the next-generation in instruments for biological sampling of the troposphere and stratosphere. Our new sampling platform ― HABITAT (High Altitude BIological Testing of the ATmosphere) ― will break new ground on several major fronts, including spatial detection and quantification of the concentration, nature, and viability of biological particles with height in the atmosphere. Due to the similarity of conditions, studying life in the Earth’s atmosphere provides a window into the possibility and nature of life which may exist in extraterrestrial systems. The experiments we propose are conceptually very simple, and technically require only routine microbiological procedures; however, several key technical advances are required to meet the extreme challenges associated with the collection of cells in the high atmosphere, which we expect to be sparsely distributed. The success of HABITAT will make significant strides towards enabling flagship level missions to planets and moons in our solar system by proving out a number of relevant technologies in an integrated test series that is representative of the temperature, pressure, and radiation conditions expected in many extraterrestrial environments. If fully successful, HABITAT may enable analysis and sample return from the atmospheres and surfaces of extraterrestrial planets or moons (e.g., Mars, Jupiter, Venus, and Titan).
Funding: LaSPACE

Past Grants:

Microbial Activity in Solid Ice: Implications for Modifying the CO2 Record in Ice Cores 
Funding: National Science Foundation, Research in Biogeosciences, 2005-09

Biological Ice Nuclei: is There a Bioprecipitation Cycle?
Funding: Louisiana State University, Office of Research and Economic Development, 2007-08

 

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