Synthesis of eukaryotic lipid biomarkers in the bacterial domain
Abstract
Lipid biomarkers are organic molecules preserved in sediments and sedimentary rocks that can function as geological proxies for certain microbial taxa or for specific environmental conditions. These molecular fossils provide a link between organisms and their environments in both modern and ancient settings and have afforded significant insight into ancient climatic events, mass extinctions, and various evolutionary transitions throughout Earth's history. However, the proper interpretation of lipid biomarkers is dependent on a broad understanding of their diagenetic precursors in modern systems. This includes understanding the taphonomic transformations that these molecules undergo, their biosynthetic pathways, and the ecological conditions that affect their cellular production. In this study, we focus on one group of lipid biomarkers - the sterols. These are polycyclic isoprenoidal lipids that have a high preservation potential and play a critical role in the physiology of most eukaryotes. However, the synthesis and function of these lipids in the bacterial domain has not been fully explored. Here we utilize a combination of bioinformatics, microbial genetics, and biochemistry to demonstrate that bacterial sterol producers are more prevalent in environmental metagenomic samples than in the genomic databases of cultured organisms and to identify novel proteins required to synthesize and modify sterols in bacteria. These proteins represent a distinct pathway for sterol synthesis exclusive to bacteria and indicate that sterol synthesis in bacteria may have evolved independently of eukaryotic sterol biosynthesis. Taken together, these results demonstrate how studies in extant bacteria can provide insight into the biological sources and the biosynthetic pathways of specific lipid biomarkers and in turn may allow for more robust interpretation of biomarker signatures.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.B32A..04W
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES;
- 1055 Organic and biogenic geochemistry;
- GEOCHEMISTRY;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY