Linking fossil climate proxies to living bacteria helps climate prediction

Amsterdam [Netherlands], December 18 (ANI): Lipids, or fat molecules, which are the building blocks of microbial skins, can be preserved as fossils that reveal details about how these organisms once lived. "A number of microbial lipids are frequently utilised to recreate historical climates.
They have always been shrouded in mystery since we don't know what bacteria produce them or under what circumstances. The ability of these molecules to forecast prior environmental circumstances is constrained by this lack of knowledge, according to Sahonero.
Her research now demonstrates which bacteria produce these lipids as well as how they have modified their lipid skin to react to environmental changes, which is another step toward more accurately recreating and forecasting climate change.
Climate reconstructions
Lipids, the molecular building blocks of the cell membrane, are unique for each microbial species. "It works just like fingerprints, they can be used to identify microbial remains," says Laura Villanueva, associate professor in the Faculty of Geosciences in Utrecht University and senior scientist at NIOZ. The lipids of ancient microbes can be found in old sediments. Once these molecules from the past are separated, identified and related to currently living groups of bacteria, the lipids can work like 'biomarkers'. These markers can tell us about the atmospheric and oceanic conditions of the ancient earth because we know from the living relatives of the microbes how they interact with their environment.
Who made these molecules and how?
For a long, it was unclear precisely which bacteria were making these specific lipids, called branched Glycerol Dialkyl Glycerol Tetraethers (GDGTs). This type of lipid is often used in climate reconstruction. Diana and her colleagues have finally discovered the bacteria forming these lipids. And also how these bacteria actually make the lipids. "It was like looking for a needle in a haystack", says Sahoreno. "From the start, we knew we had to answer this question with a massive approach. We needed to investigate more than 1850 proteins to identify microbes making these lipid molecules."
Once researchers know which currently living bacteria make these lipid molecules, they can be used to make more accurate climate reconstructions. Researchers can measure the interactions of these living bacteria with their surrounding seawater or atmosphere. This information leads to 'proxies' - keys to correlate details of the lipid molecules (abundance for instance) to values of the environment. This is an important step in reconstructing past environmental and climate conditions, based on old sediment samples.
Early evolution of life
"Our study indicates that there are many species of currently living bacteria that can make these types of membrane lipids. Also, we found that those bacteria are all limited to environments where oxygen is absent," says Sahonero. "This study into archaeal-like lipids of bacteria shows how this group of microbes that produces them evolved their lipid membrane billions of years ago. It is fantastic to get a glimpse of this part of life's history. It was mostly a mystery until now."
What next?
The work of Sahonero and her colleagues is still ongoing. "Now we know which bacteria form these molecular building blocks and we understand how they do that. Next, we need to find out how the production of these molecules depends on environmental factors like water temperature or pH," says Villanueva. "Then, the proxy based on these bacterial lipids can be used more confidently by (paleo)climatologists. This gives them new possibilities to reconstruct and predict climate change in more detail." (ANI)