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Project Progress

Advancing Methods for the Analyses of Organics Molecules in Microbial Ecosystems

GCA Annual Report 2010

GCA Investigator: Jennifer Eigenbrode

Collaborators: Fabien Stalport, GSFC; Daniel Glavin, GSFC; Melissa Floyd, GSFC; Linda Jahnke, NASA Ames; Eric Roden, Univ. Wisconsin; Dave Emerson, Bigelow Oceanographic Institute; Roger Summons, MIT; Christian Hallmann, MIT; John Valley, Univ. Wisconsin.

Students:

Eigenbrode’s astrobiological interest focuses on understanding the formation and preservation of organic and isotopic sedimentary records of ancient Earth and Mars. These studies present sampling and analytical challenges that are ancient rock- or habitat-specific. Eigenbrode seeks to overcome these challenges with modification and development of contamination tracking, sampling, and analytical methods (primarily GCMS) that improve the recovery of meaningful observations and provide protocol guidance for future astrobiological missions.

Advancing protocols for organic molecular studies of iron-oxide rich sediments
Eigenbrode has been developing thermochemolysis methodologies for extracting components of complex organics molecules from samples that pose unique analytical challenges because of their mineral composition. These include iron-oxide rich samples regarded as analogs to ancient aqueous environments on Mars and ancient Earth, as well as perchlorate-laden samples. The challenge in these cases is that the mineral oxidants can both chelate or ionically bond with the organics making them difficult to extract by traditional methods and contribute to partial or complete destruction of organic molecules over time (as in the rock record) or during traditional thermal extraction (in the lab).

The samples set from 2009, which included samples from neutral-pH groundwater iron seeps and acidic river terrace sediments from the Rio Tinto, Spain, have been expanded in 2010 to include culture and sediment samples from an iron-oxide rich hydrothermal spring (Chocolate Pots, Yellowstone, provided by Linda Jahnke, NASA Ames) and iron concretions from Lake Tyrrell, Australia (provided by Eric Roden, Univ. Wisconsin, and Dave Emerson, Bigelow Oceanographic Institute).

Thermochemolysis is performed using an automated system that handles samples up to 500 mg and introduces products to either a hydrocarbon trap or directly onto a gas chromatographic column for analysis by a mass spectrometer. The primary challenge is in optimizing the gas flow system so that the chemical reagents (e.g. tetramethylammonium hydroxide in methanol) do not overwhelm the analyte of interest during separation or detection. Results from analog samples and standard chemicals reveal that product composition is partially dependent on the temperature of the thermochemolysis step. Heterocyclic and functionalized PAH compounds tend to form multiple products making it difficult to trace back to the original structures.

Thermochemolysis of biological proteins and membranes and sedimentary samples have yielded amine, aldehyde, ketone, and methyl ester derivatives. In some samples the distribution of membrane lipid derivatives have provided unique insight into the occurrence of bacterial methylhopanoids. This observation warrants further research as it has a bearing on a new approach to effective lipid analysis and our understanding of methylhopanoids in microbial ecology on modern and, perhaps, ancient Earth. With further optimization, the thermochemolysis method will be aptly suited for in situ analyses at terrestrial field sites and future space flight missions that have instrumentation for molecular detection.

The above investigations meet NAI objectives (5.1) Environment-dependent, molecular evolution in microorganisms, (5.3) Biochemical adaptation to extreme environments, (6.1) Effects of environmental changes on microbial ecosystems, and (7.1) Biosignatures to be sought in Solar System materials; and may have implications for objectives (2.1) Mars exploration and (4.1) Earth’s early biosphere.

Carbon Isotopic Records of the Neoarchean
Eigenbrode is collaborating with colleagues of the NAI MIT (Roger Summons et al.) and Wisconsin (John Valley et al.) teams to understand the spatial and molecular variations in stable carbon isotopes of sedimentary organic matter in the 2.7 to 2.5 Ga sedimentary record of Neoarchean Hamersley Province. This record marks a crux of Earth’s early history in which redox and chemical conditions of environments and atmosphere were evolving to a more oxidized state. Christian Hallmann, MIT postdoc, is planning on doing most analyses. This project is just getting started and is in the preliminary analysis phase. It will require method development and innovative analytical approaches that employ the CAMECA 1280 Ion Microprobe at Univ. Wisconsin and compound-specific isotope analysis (CSIA) at MIT and GSFC. This goal for this project is to understand how microbial inputs having a very broad isotopic range are preserved and altered in the Archean record.

The above studies meet NAI objectives (4.1) Earth’s early biosphere, (5.1) Environment-dependent, molecular evolution in microorganisms, and (5.2) Co-evolution of microbial communities.

Publications and Literature Contributions:
Eigenbrode, Jennifer, accepted, Isoprenoids, in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Eigenbrode, Jennifer, accepted, Steranes, in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Eigenbrode, Jennifer, accepted, Hopanes, in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Eigenbrode, Jennifer, accepted, Geological Record of Molecular Fossils in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Eigenbrode, Jennifer, accepted, Geological Record of Carboxylic Acids, in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Eigenbrode, Jennifer, accepted, Geological Record of Fatty Acids, in Encyclopedia of Astrobiology, Muriel Gargaud et al. (eds.), Springer-Verlag Berlin Heidelberg, DOI 10.1007/978-3-642-11274-4.
Summons, R.E., Amend, J.P., Bish, D., Buick, R., Cody, G.D., Des Marais, D.J., Dromart, G., Eigenbrode, J.L., Knoll, A.H., Sumner, D.Y, submitted, Preservation of Martian Organic & Environmental Records, Astrobiology