Novel Extended Tetraether Lipids Found in a High-CO₂ Geyser

Area of Science:

• Geochemistry
• Microbiology
• Biogeochemistry

Background:

• Archaea exhibit diverse lipid structures, particularly isoprenoidal glycerol dialkyl glycerol tetraethers (iGDGTs), crucial for membrane adaptation in extreme environments.
• Previous research predicted tetraether synthesis in Candidatus Altiarchaeum based on metagenomic data.

Purpose of the Study:

• To comprehensively analyze the archaeal lipidome of the CO2-rich, cold-water Geyser Andernach.
• To identify novel iGDGT structures and understand their role in archaeal adaptation.

Main Methods:

• Ultra-high-resolution mass spectrometry was employed for lipidome analysis.
• Lipid identification and characterization were performed on samples from Geyser Andernach.

Main Results:

• Detected iGDGT-0, supporting the tetraether synthesis capability of Candidatus Altiarchaeum.
• Discovered novel extended iGDGTs and iGTGTs with asymmetrical isoprenoid additions.
• Identified the potential absence of GDGT ring synthase genes in the producing archaea's genome.

Conclusions:

• The novel extended iGDGTs may serve as a membrane adaptation strategy for archaea in nutrient-depleted geyser environments.
• This discovery highlights the remarkable adaptive flexibility of archaea in extreme physicochemical conditions.