NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Lipid Biomarkers for a Hypersaline Microbial Mat CommunityThe use of lipid biomarkers and their carbon isotopic compositions are valuable tools for establishing links to ancient microbial ecosystems. Various lipids associated with specific microbial groups can serve as biomarkers for establishing organism source and function in contemporary microbial ecosystems (membrane lipids), and by analogy, potential relevance to ancient organic-rich sedimentary rocks (geolipids). As witnessed by the stromatolite record, benthic microbial mats grew in shallow water lagoonal environments. Our recent work has focused on lipid biomarker analysis of a potential analogue for such ancient mats growing in a set of hypersaline evaporation ponds at Guerrero Negro, Baja California Sur, Mexico. The aerobic, surface layer of this mat (0 to 1 mm) contained a variety of ester-bound fatty acids (FA) representing a diverse bacterial population including cyanobacteria, sulphate reducers (SRB) and heterotrophs. Biomarkers for microeukaryotes detected in this layer included sterols, C-20 polyunsaturated FA and a highly branched isoprenoid, diagnostic for diatoms. Cyanobacteria were also indicated by the presence of a diagnostic set of mid-chain methylalkanes. C-28, to C-34 wax esters (WXE) present in relatively small amounts in the upper 3 mm of the mat are considered biomarkers for green non-sulphur bacteria. Ether-bound isoprenoids were also identified although in considerably lower abundance than ester-bound FA (approx. 1:l0). These complex ether lipids included archatol, hydroxyarchaeol and a C-40 tetraether, all in small amounts. After ether cleavage with boron tribromide, the major recovered isoprenyl was a C-30:1. This C(sub 30;1) yelded squalane after hydrogenation, a known geobiomarker for hypersaline environments in ancient oils and sediments. In this mat, it represents the dominant Archaeal population. The carbon isotopic composition of biomarker lipids were generally depleted relative to the bulk organic material (delta C-13 TOC -10%). Most depleted were the cyanobacterial methylalkanes at -27% with FA such as the SRB biomarker, 10- methyl C-I6, somewhat heavier at -16%, and WXE at -17%. The C-30:1 isoprenyl was most enriched with delta C-13 in the -7 to -11% range, much too heavy to represent the methanogen population responsible for mat methane values measured at -60%.
Document ID
20040081071
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Jahnke, Linda
(NASA Ames Research Center Moffett Field, CA, United States)
Orphan, Victoria
(NASA Ames Research Center Moffett Field, CA, United States)
Embaye, Tsegereda
(Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Turk, Kendra
(California Univ. Santa Cruz, CA, United States)
Kubo, Mike
(Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Summons, Roger
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
August 21, 2013
Publication Date
March 3, 2004
Subject Category
Life Sciences (General)
Meeting Information
Meeting: Astrobiology Science Conference
Location: Moffett Field, CA
Country: United States
Start Date: March 28, 2004
End Date: April 1, 2004
Funding Number(s)
PROJECT: RTOP 344-58-92-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available