|
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.
|
 |
 |
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
|
