Microbial lipids betrayed by their fossils

Area of Science:

• Biogeochemistry
• Microbial Ecology
• Organic Geochemistry

Background:

• Microbial lipids, particularly hopanoids and orphan lipids, are crucial components of cell membranes.
• These lipids play a significant role in membrane reinforcement and stability across diverse microbial communities.
• Understanding the evolutionary origins and relationships of these lipids is essential for interpreting ancient biomolecular records.

Purpose of the Study:

• To identify and characterize novel families of microbial lipids based on their molecular fossil records.
• To investigate the universal role of polyterpenoids, including hopanoids, in microbial membrane reinforcement.
• To propose a hypothetical phylogenetic tree illustrating the evolutionary connections between various microbial lipids and cholesterol.

Main Methods:

• Analysis of molecular fossils to identify and characterize lipid structures.
• Comparative analysis of lipid structures across different microbial taxa.
• Phylogenetic reconstruction based on structural similarities and postulated intermediates.

Main Results:

• Discovery of novel families of microbial lipids, including widespread hopanoids and distinct 'orphan' lipids.
• Evidence supporting the universal function of these polyterpenoids in reinforcing microbial membranes.
• A proposed phylogenetic framework linking hopanoids and orphan lipids to bacterial carotenoids, cycloartenol, and cholesterol.

Conclusions:

• Molecular fossils provide critical insights into the diversity and evolution of microbial lipids.
• Polyterpenoids are fundamental to microbial membrane structure and function across a broad phylogenetic spectrum.
• The proposed phylogenetic tree offers a new perspective on the evolutionary history of lipids, connecting microbial and eukaryotic pathways.