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Title: GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean

Abstract

Glycerol dibiphytanyl glycerol tetraethers (GDGTs) are distinctive archaeal membrane-spanning lipids with up to eight cyclopentane rings and/or one cyclohexane ring. The number of rings added to the GDGT core structure can vary as a function of environmental conditions, such as changes in growth temperature. This physiological response enables cyclic GDGTs preserved in sediments to be employed as proxies for reconstructing past global and regional temperatures and to provide fundamental insights into ancient climate variability. Yet, confidence in GDGT-based paleotemperature proxies is hindered by uncertainty concerning the archaeal communities contributing to GDGT pools in modern environments and ambiguity in the environmental and physiological factors that affect GDGT cyclization in extant archaea. To properly constrain these uncertainties, a comprehensive understanding of GDGT biosynthesis is required. Here, we identify 2 GDGT ring synthases, GrsA and GrsB, essential for GDGT ring formation in Sulfolobus acidocaldarius . Both proteins are radical S-adenosylmethionine proteins, indicating that GDGT cyclization occurs through a free radical mechanism. In addition, we demonstrate that GrsA introduces rings specifically at the C-7 position of the core GDGT lipid, while GrsB cyclizes at the C-3 position, suggesting that cyclization patterns are differentially controlled by 2 separate enzymes and potentially influenced by distinct environmentalmore » factors. Finally, phylogenetic analyses of the Grs proteins reveal that marine Thaumarchaeota, and not Euryarchaeota, are the dominant source of cyclized GDGTs in open ocean settings, addressing a major source of uncertainty in GDGT-based paleotemperature proxy applications.« less

Authors:
ORCiD logo; ; ; ; ORCiD logo; ORCiD logo; ORCiD logo
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1569769
Grant/Contract Number:  
FG02-02ER15296
Resource Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Name: Proceedings of the National Academy of Sciences of the United States of America; Journal ID: ISSN 0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Country of Publication:
United States
Language:
English

Citation Formats

Zeng, Zhirui, Liu, Xiao-Lei, Farley, Kristen R., Wei, Jeremy H., Metcalf, William W., Summons, Roger E., and Welander, Paula V. GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean. United States: N. p., 2019. Web. doi:10.1073/pnas.1909306116.
Zeng, Zhirui, Liu, Xiao-Lei, Farley, Kristen R., Wei, Jeremy H., Metcalf, William W., Summons, Roger E., & Welander, Paula V. GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean. United States. doi:10.1073/pnas.1909306116.
Zeng, Zhirui, Liu, Xiao-Lei, Farley, Kristen R., Wei, Jeremy H., Metcalf, William W., Summons, Roger E., and Welander, Paula V. Mon . "GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean". United States. doi:10.1073/pnas.1909306116.
@article{osti_1569769,
title = {GDGT cyclization proteins identify the dominant archaeal sources of tetraether lipids in the ocean},
author = {Zeng, Zhirui and Liu, Xiao-Lei and Farley, Kristen R. and Wei, Jeremy H. and Metcalf, William W. and Summons, Roger E. and Welander, Paula V.},
abstractNote = {Glycerol dibiphytanyl glycerol tetraethers (GDGTs) are distinctive archaeal membrane-spanning lipids with up to eight cyclopentane rings and/or one cyclohexane ring. The number of rings added to the GDGT core structure can vary as a function of environmental conditions, such as changes in growth temperature. This physiological response enables cyclic GDGTs preserved in sediments to be employed as proxies for reconstructing past global and regional temperatures and to provide fundamental insights into ancient climate variability. Yet, confidence in GDGT-based paleotemperature proxies is hindered by uncertainty concerning the archaeal communities contributing to GDGT pools in modern environments and ambiguity in the environmental and physiological factors that affect GDGT cyclization in extant archaea. To properly constrain these uncertainties, a comprehensive understanding of GDGT biosynthesis is required. Here, we identify 2 GDGT ring synthases, GrsA and GrsB, essential for GDGT ring formation in Sulfolobus acidocaldarius . Both proteins are radical S-adenosylmethionine proteins, indicating that GDGT cyclization occurs through a free radical mechanism. In addition, we demonstrate that GrsA introduces rings specifically at the C-7 position of the core GDGT lipid, while GrsB cyclizes at the C-3 position, suggesting that cyclization patterns are differentially controlled by 2 separate enzymes and potentially influenced by distinct environmental factors. Finally, phylogenetic analyses of the Grs proteins reveal that marine Thaumarchaeota, and not Euryarchaeota, are the dominant source of cyclized GDGTs in open ocean settings, addressing a major source of uncertainty in GDGT-based paleotemperature proxy applications.},
doi = {10.1073/pnas.1909306116},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1073/pnas.1909306116

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Works referenced in this record:

Sulfolobus: A new genus of sulfur-oxidizing bacteria living at low pH and high temperature
journal, January 1972

  • Brock, Thomas D.; Brock, Katherine M.; Belly, Robert T.
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Biosynthesis of Ether-Type Polar Lipids in Archaea and Evolutionary Considerations
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