Lipid biomarkers: molecular tools for illuminating the history of microbial life

Fossilized lipids preserved in sedimentary rocks offer singular insights into the Earth's palaeobiology. These 'biomarkers' encode information pertaining to the oxygenation of the atmosphere and oceans, transitions in ocean plankton, the greening of continents, mass extinctions and climate change. Historically, biomarker interpretations relied on inventories of lipids present in extant microorganisms and counterparts in natural environments. However, progress has been impeded because only a small fraction of the Earth's microorganisms can be cultured, many environmentally significant microorganisms from the past no longer exist and there are gaping holes in knowledge concerning lipid biosynthesis. The revolution in genomics and bioinformatics has provided new tools to expand our understanding of lipid biomarkers, their biosynthetic pathways and distributions in nature. In this Review, we explore how preserved organic molecules provide a unique perspective on the history of the Earth's microbial life. We discuss how advances in molecular biology have helped elucidate biomarker origins and afforded more robust interpretations of fossil lipids and how the rock record provides vital calibration points for molecular clocks. Such studies are open to further exploitation with the expansion of sequenced microbial genomes in accessible databases. Lipid biomarkers provide insights into the nature and history of the Earth's microbial life. In this Review, Summons et al. discuss how advances in molecular biology have helped elucidate lipid biomarker origins and afforded robust interpretations of fossil lipids, and explore key examples of how genomics-enabled advances in lipid biomarker science are illuminating the history of microbial life on the Earth.

Automated summary

Fossilized lipids in sedimentary rocks provide unique insights into Earth's microbial life history, offering information on atmospheric and ocean oxygenation, ocean plankton transitions, continent greening, mass extinctions, and climate change. Advances in molecular biology have helped elucidate the origins of lipid biomarkers, leading to more robust interpretations of fossil lipids and providing vital calibration points for molecular clocks in the rock record. Exploitation of sequenced microbial genomes in accessible databases presents further opportunities for lipid biomarker studies.