Horizontal gene transfer constrains the timing of methanogen evolution

Area of Science:

• Astrobiology
• Geochemistry
• Microbial Evolution

Background:

• Microbial methanogenesis may have regulated early Earth's climate, crucial for a liquid hydrosphere under a faint young Sun.
• Determining the origin of microbial methanogenesis is key to understanding early Earth's habitability but is hampered by scarce evidence.
• Existing geochemical and fossil records are insufficient to accurately date microbial methanogenesis.

Purpose of the Study:

• To establish a more precise timeline for the evolution of microbial methanogenesis.
• To provide independent evidence supporting the role of methane in early Earth's climate regulation.
• To overcome limitations of previous dating methods for early microbial life.

Main Methods:

• Utilized a horizontal gene transfer event between archaeal methanogens and the ancestor of Cyanobacteria as a temporal calibration point.
• Employed molecular clock analyses, calibrated by this specific gene transfer event.
• Leveraged the fossil record of Cyanobacteria to anchor the molecular clock.

Main Results:

• Molecular clock analyses indicate methanogens diverged within Euryarchaeota no later than 3.51 billion years ago.
• Methanogenesis likely evolved even earlier than the divergence of methanogens.
• This provides a new temporal constraint for the evolution of methane-producing microbes.

Conclusions:

• The findings support the hypothesis that microbial methane production played a significant role in maintaining early Earth's temperature.
• This research offers a novel method for dating ancient microbial processes using horizontal gene transfer events.
• The established timeline strengthens the link between microbial methanogenesis and the maintenance of a habitable early Earth.