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Linking molecular taxonomy with environmental geochemsitry in environments relevant to astrobiology: The anaerobic oxidation of methane in cold seeps & deeply buried marine sediments

House, Christopher H. and Biddle, Jennifer F. and Lipp, Julius S. and Orphan, Victoria J. and McKeegan, Kevin D. and Hinrichs, Kai-Uwe (2006) Linking molecular taxonomy with environmental geochemsitry in environments relevant to astrobiology: The anaerobic oxidation of methane in cold seeps & deeply buried marine sediments. Origins of life and evolution of the biosphere, 36 (3). pp. 314-315. ISSN 0169-6149. https://resolver.caltech.edu/CaltechAUTHORS:20140723-162327093

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Abstract

The linking of molecular taxonomy (including 16s rRNA) to environmental geochemistry is a powerful way to work out the interactions, metabolic activities, and food webs of microorganisms in their natural setting, whether it is sediment, soil, or a water column. To this end, we developed a method for coupling an extant microorganism’s genetic information with geochemical data derived from the direct analysis of its cell. FISH–SIMS combines fluorescent in-situ hybridization (FISH) with secondary ion mass spectrometry (SIMS). FISH is a culture-independent technique used to visually identify naturally occurring microorganisms by staining their ribosomal RNA. Secondary ion mass spectrometry (SIMS) is a method by which geochemical information can be obtained from microsamples. Using FISH-SIMS, a researcher can measure a target cell’s isotopic or elemental composition in a mixed environment. The identification and study of methane-consuming microorganisms is an important step toward understanding the methane cycle and microbial response to methane release. The recent identification of two distinct Archaea capable of anaerobic methane oxidationwas in part accomplished using FISH-SIMS. Because natural methane is highly depleted in 13C, FISH-SIMS is particularly powerful at determining if a particular cell, collected from the environment, and consumed methane as a substrate for its cell carbon. This research demonstrated that both the ANME-1 and ANME–2 Archaea from the Eel River Methane Seep are highly depleted in 13C due to growth on methane. The deep marine biosphere is thought to contain abundant microbial inhabitants, estimated to be a tenth of the Earth’s total biomass. Sediments from this environment were recovered during Ocean Drilling Program (ODP) Leg 201, and were analyzed by both molecular biological and organic geochemical techniques. Of particular interest in these sediments were four sulfate/methane transition zones seen at ODP Sites 1227, 1229 and 1230, two of which coincided with strongly elevated cell counts. Archaeal cells in these zones were analyzed for abundance and d13C composition by whole cell analysis (FISH-SIMS) and intact membrane lipids (HPLC-ESI-MSn). Cell counts showed greater archaeal abundance than bacterial, which was reflected by intact membrane lipid abundance. Isotopic compositions by both techniques (often around −20‰) suggest that methane is not an important carbon source for these cells. Autotrophic carbon fixation appears to be an unlikely metabolism given the relationship between the isotopic composition of DIC and archaeal biomass. The isotopic evidence suggests that the bulk archaeal community is heterotrophic, possibly mediating the oxidation of methane without consuming it as a carbon source. The importance of these techniques is that the cells targeted for study can be environmental species that cannot currently be grown in the laboratory. These techniques promises to become critical for working out the interactions, metabolic activities, and food webs of microorganisms in their natural setting, whether it is sediment, soil, or a water column.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://link.springer.com/journal/11084/36/3/page/1PublisherAbstracts
ORCID:
AuthorORCID
House, Christopher H.0000-0002-4926-4985
Orphan, Victoria J.0000-0002-5374-6178
Hinrichs, Kai-Uwe0000-0002-0739-9291
Additional Information:© 2006 Springer.
Issue or Number:3
Record Number:CaltechAUTHORS:20140723-162327093
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140723-162327093
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47446
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:24 Jul 2014 15:44
Last Modified:09 Mar 2020 13:18

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