| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | February 11, 2014 |
| Latest Amendment Date: | February 11, 2014 |
| Award Number: | 1418831 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Enriqueta Barrera
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | February 15, 2014 |
| End Date: | August 31, 2015 (Estimated) |
| Total Intended Award Amount: | $120,838.00 |
| Total Awarded Amount to Date: | $120,838.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
450 JANE STANFORD WAY STANFORD CA US 94305-2004 (650)723-2300 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
CA US 94305-2210 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Geobiology & Low-Temp Geochem |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The majority of life's history had been dominated by microbes whose metabolic inventions have significantly altered the Earth's surface environment and, in turn, impacted the evolution of life on Earth. Yet our ability to study microbial life in the context of the Earth's distant past has remained a difficult challenge primarily because microbes do not readily leave diagnostic morphological fossils. One of the predominant strategies to overcome this challenge has been the use of "molecular fossils." This approach correlates the occurrence of preserved lipids in ancient rocks with their production in modern bacteria. Two sets of lipids that have emerged as powerful geological biomarkers are sterols, produced primarily by eukaryotes, and the sterol-like hopanoids, produced only by bacterial species. In this project, investigators will study the biosynthesis and physiological function of both of these lipids in Methylococcus capsulatus. The ability to produce both sets of lipids is rarely observed in the bacterial domain. Therefore, this organism provides an excellent model system for examining the evolutionary and physiological significance of both hopanoids and sterols with the expectation that these studies will allow for a more informed and robust interpretation of the occurrence of sterols and hopanoids in the rock record. These studies will be carried out through a collaborative effort merging the fields of microbiology and organic geochemistry. The project will train an early career research scientist from an underrepresented minority group and a graduate student in the interdisciplinary field of geobiology.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Sterol lipids, such as cholesterol, are an important biological feature of eukaryotic organisms (e.g. animals, plants, fungi). These lipids are necessary for maintaining membrane function and play a role in cell development and cell signaling. Furthermore, sterols are quite recalcitrant and are often preserved in the rock record where they can act as molecular fossils for ancient eukaryotic organisms. Thus, there is an interest in understanding sterol biosynthesis and function from biologist and geologist alike.
It is often thought that sterol production is restricted to more complex organisms (i.e. eukaryotes) and that bacteria do not produce nor require these lipids. However, a few bacterial species have been shown to produce sterols and the physiological and geological implications of this bacterial production is unknown. In this study, we set out to understand several aspects of sterol biology in bacteria - what bacterial organisms produce sterols, what proteins are involved in their production and what their physiological role may be. Through bioinformatic analyses where we compared genomes of various bacterial and eukaryotic species, we were able to identify sterol biosynthesis proteins in bacteria that are distinct from what has been observed in eukaryotes. Further, we identified a diverse group of bacterial species that have genes in their genomes that would indicate sterol production. We tested several of these strains and shown that they do produce a variety of sterols. Finally, through our lipid survey of potential sterol producers, we have demonstrated the production of another sterol-like lipid, tetrahymanol, in a subset of methane consuming bacteria. Through this discovery, we were able to uncover tetrahymanol production in a variety of bacterial species and discover a distinct tetrahymanol synthesis pathway in bacteria. The study of sterol and other cyclic lipids like tetrahymanol in bacteria will provide context for understanding the evolutionary history of these molecules which in turn will be useful for properly interpreting the occurrence of these lipids in the rock record.
Finally, through this project, one postdoctoral scholar, one graduate student and one undergraduate student were trained in bacterial physiology, genetics and lipid analysis. Further, students were introduced to the interdisciplinary field of geobiology and learned how biological lab based studies could inform and address geologically relevant questions.
Last Modified: 09/08/2015
Modified by: Paula V Welander
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