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Lipid biomarkers for bacterial ecosystems: studies of cultured organisms, hydrothermal environments and ancient sedimentsThis paper forms part of our long-term goal of using molecular structure and carbon isotopic signals preserved as hydrocarbons in ancient sediments to improve understanding of the early evolution of Earth's surface environment. We are particularly concerned with biomarkers which are informative about aerobiosis. Here, we combine bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems to construct models for the nature, behaviour and preservation potential of primitive microbial communities. We use a combined molecular and isotopic approach to characterize lipids produced by cultured bacteria and test a variety of culture conditions which affect their biosynthesis. This information is then compared with lipid mixtures isolated from contemporary hot springs and evaluated for the kinds of chemical change that would accompany burial and incorporation into the sedimentary record. In this study we have shown that growth temperature does not appear to alter isotopic fractionation within the lipid classes produced by a methanotropic bacterium. We also found that cultured cyanobacteria biosynthesize diagnostic methylalkanes and dimethylalkanes with the latter only made when growing under low pCO2. In an examination of a microbial mat sample from Octopus Spring, Yellowstone National Park (USA), we could readily identify chemical structures with 13C contents which were diagnostic for the phototrophic organisms such as cyanobacteria and Chloroflexus. We could not, however, find molecular evidence for operation of a methane cycle in the particular mat samples we studied.
Document ID
20040173288
Document Type
Reprint (Version printed in journal)
Authors
Summons, R. E. (Australian Geological Survey Organisation, Canberra, Australia)
Jahnke, L. L.
Simoneit, B. R.
Date Acquired
August 22, 2013
Publication Date
January 1, 1996
Publication Information
Publication: Ciba Foundation symposium
Volume: 202
ISSN: 0300-5208
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
Non-NASA Center
NASA Center ARC
Review
Review, Tutorial