Bacteria living in lakes and peatlands produce microscopic lipid molecules that survive in sediment for up to a billion years, and this project will identify which bacteria make them and why. These lipids—called brGMGTs—were recently discovered to change their chemical structure in response to temperature, making them a promising tool for reconstructing past land temperatures. But no one knows which bacteria produce them, what triggers their production, or how reliably they track temperature. Without that fundamental knowledge, the lipids remain an intriguing but unusable climate clue. The team will combine microbiology, organic geochemistry, and computer simulations to find the gene responsible, isolate and culture the bacteria, and calibrate the temperature signal in the lab. If successful, this will give palaeoclimatologists a robust method to read land-temperature records from ancient sediments—filling a gap that ocean sediments cannot address. This is primarily fundamental science: understanding microbial adaptation and lipid biosynthesis. But a reliable land-temperature proxy would allow scientists to compare past warming events with today’s climate change, potentially improving projections of future impacts on terrestrial ecosystems and human societies.
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Imagine using tiny, molecular fossils that cannot be seen with the naked eye as a tool to reveal Earth’s climate story as it unfolded on land. Understanding how land temperatures evolved is critical. Yet ocean sediments have long been our main source of ancient climate data, leaving the land’s history – the terrestrial past - largely untold. This project will change that by bringing together scientist from the UK (Bristol) and US (Stanford) to study fundamental microbial processes and develop new methods to unlock climate information hidden in recently discovered molecular fossils. Bacteria have an extraordinary way of adapting to environmental stress by altering the lipids that make up their cell membranes. These lipids can be preserved for a billion year as molecular fossils. This project focuses on a recently discovered type of bacterial membrane lipids called branched glycerol monoalkyl glycerol tetraethers (brGMGTs in short), which are abundant in lakes and peatlands. Two recent papers suggested that the relative abundance and distribution of brGMGTs depends on temperature in lakes and peatlands. These landmark papers suggested that brGMGTs hold great potential as new terrestrial temperature proxy. However, the specific bacteria that produce these compounds, why they produce them, their exact temperature dependence, and why they produce different types of these compounds in response to different temperatures, is unknown. These fundamental gaps are limiting our ability to use brGMGT lipids as tools for terrestrial climate reconstruction. This project will combine the latest microbiology, organic geochemistry, and computational-chemistry methods to answer these fundamental questions. The project begins with identifying the gene responsible for brGMGT production, using this information to isolate and culture bacteria that carry this gene, and as result, for the first time, identify the bacterial source organism of brGMGTs, lipids that are widespread in the environment. We will then develop a culture-based temperature calibration, growing brGMGT-producing bacteria under different conditions in the lab. Lastly, we will develop state-of-the-art computer simulations to determine the role of brGMGTs in bacterial membranes. By understanding which bacteria make brGMGTs and exactly how and why they modify their membranes with these lipids, we will create crucial insights into pathways of microbial adaptation and develop a robust tool to quantify past temperature changes on land. The implications are far-reaching for palaeoclimatology and organic geochemistry, equipping researchers with a powerful new way to reconstruct Earth’s climate past. With this information, scientists could compare ancient warming events and greenhouse worlds with today’s rapid changes, potentially aiding future impacts of anthropogenic climate change. We will also develop novel methods for microbiologists and computational chemists to explore lipid biosynthesis and dynamics. This will open exciting new scientific ground by offering a deep comprehension of how microbes adapt to environmental stressors and how and why membrane lipids are made. Understanding the genetic and biochemical mechanisms behind these adaptations not only advances our knowledge of microbial resilience and evolution but also sheds light on their role in Earth’s System. In summary, this project is not just about filling in the gaps of Earth’s climate history; it’s about bringing together a unique team and using state-of-the-art multidisciplinary methods to develop a precise tool to quantify how the climate on land has shaped—and continues to shape—our world together with creating a fundamental understanding of the microbial and molecular dynamics that underpin this tool.
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