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Sources of organic nitrogen at the serpentinite-hosted Lost City hydrothermal field.
MedLine Citation:
PMID:  23346942     Owner:  NLM     Status:  Publisher    
The reaction of ultramafic rocks with water during serpentinization at moderate temperatures results in alkaline fluids with high concentrations of reduced chemical compounds such as hydrogen and methane. Such environments provide unique habitats for microbial communities capable of utilizing these reduced compounds in present-day and, possibly, early Earth environments. However, these systems present challenges to microbial communities as well, particularly due to high fluid pH and possibly the availability of essential nutrients such as nitrogen. Here we investigate the source and cycling of organic nitrogen at an oceanic serpentinizing environment, the Lost City hydrothermal field (30°N, Mid-Atlantic Ridge). Total hydrolizable amino acid (THAA) concentrations in the fluids range from 736 to 2300 nm and constitute a large fraction of the dissolved organic carbon (2.5-15.1%). The amino acid distributions, and the relative concentrations of these compounds across the hydrothermal field, indicate they most likely derived from chemolithoautotrophic production. Previous studies have identified the presence of numerous nitrogen fixation genes in the fluids and the chimneys. Organic nitrogen in actively venting chimneys has δ(15) N values as low as 0.1‰ which is compatible with biological nitrogen fixation. Total hydrolizable amino acids in the chimneys are enriched in (13) C by 2-7‰ compared to bulk organic matter. The distribution and absolute δ(13) C(THAA) values are compatible with a chemolithoautotrophic source, an attribution also supported by molar organic C/N ratios in most active chimneys (4.1-5.5) which are similar to those expected for microbial communities. In total, these data indicate nitrogen is readily available to microbial communities at Lost City.
S Q Lang; G L Früh-Green; S M Bernasconi; D A Butterfield
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-25
Journal Detail:
Title:  Geobiology     Volume:  -     ISSN:  1472-4669     ISO Abbreviation:  Geobiology     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101185472     Medline TA:  Geobiology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© 2013 Blackwell Publishing Ltd.
Department of Earth Sciences, ETH Zürich, Zurich, Switzerland.
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