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.
