A non-methanogenic archaeon within the order Methanocellales

Area of Science:

• Microbiology
• Geochemistry
• Astrobiology

Background:

• Serpentinization creates unique, ultra-reducing environments on Earth.
• Certain archaea, like Methanocellales, are known methane producers in these settings.

Purpose of the Study:

• To investigate microbial life in serpentinized springs.
• To characterize a novel archaeon from The Cedars, California.
• To determine the metabolic capabilities of the Met12 archaeon.

Main Methods:

• Metagenomic sequencing to assemble a complete genome.
• In situ transcriptomic analysis to study gene expression.
• Heterologous protein expression in a model bacterium.

Main Results:

• A circularized metagenome-assembled genome (Met12) was constructed.
• Met12 lacks key genes for methanogenesis but possesses an acetyl-CoA pathway.
• A multi-heme c-type cytochrome was highly expressed and shown to accept electrons.

Conclusions:

• Met12 is identified as a carbon dioxide-reducing, electron-fueled acetogen, not a methanogen.
• This finding expands our understanding of microbial metabolism in serpentinizing environments.
• The study highlights a novel form of microbial energy metabolism without electron bifurcation.