Tracing the origin of marine sedimentary hopanoids using compound-specific multi-istope analysis and metagenomics

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Bacterial hopanoids are among the most diagnostic lipid biomarkers found almost universally in the sedimentary record. They have an excellent but as yet unfulfilled potential to be a rich source of information in the study of microbial processes and ecology as well as indicators of environmental conditions within recent and ancient systems (linked to climate change). However, their environmental, physiological, and taxonomic origins remain elusive and the most basic questions about the origin of marine sedimentary hopanoids remain unanswered. It is unknown whether most hopanoids derived from the marine microbial population or are imported as part of the terrigenous organic matter flux. Likewise, it remains uncertain whether most hopanoids are the products of bacterial primary producers or products of the heterotrophic community responsible for organic matter degradation and accordingly whether their structural and isotopic diversity is related to the diversity of hopanoid producers in the environment. To answer these questions, this project takes an interdisciplinary approach combining compound-specific multi-isotope analysis complemented by metagenomics to unravel the origins of hopanoids in marine sediments. The results obtained in this project will help to evaluate the critical interpretation of paleoenvironmental conditions and the status of paleoecological communities. An improved understanding of the relative sedimentation of primary and secondary productivity and the interactions between the terrigenous and marine carbon reservoirs also will yield information critical to our understanding of the global carbon cycle.