How to make a living by exhaling methane

Area of Science:

• Microbiology and Biochemistry
• Prokaryotic Metabolism
• Biogeochemical Cycles

Background:

• Methane (CH4) is a significant greenhouse gas produced by microorganisms in the biosphere.
• Two primary metabolic routes contribute to biological methane production.
• Understanding these pathways is crucial for microbial ecology and global carbon cycling.

Purpose of the Study:

• To delineate the distinct biochemical pathways of methane production in prokaryotes.
• To compare the initial steps and energy conservation mechanisms of aceticlastic and CO2 reduction pathways.
• To highlight the distribution of these pathways across bacterial and archaeal domains.

Main Methods:

• Comparative analysis of biochemical pathways for methane (CH4) synthesis.
• Identification of unique enzymes and steps in aceticlastic and CO2 reduction pathways.
• Review of microbial distribution of these metabolic strategies across Archaea and Bacteria.

Main Results:

• The aceticlastic pathway, converting acetate to CH4, accounts for at least two-thirds of biogenic methane.
• The carbon dioxide (CO2) reduction pathway, using H2, formate, or CO, accounts for approximately one-third.
• CO2 reduction pathway enzymes are specific to Archaea, while aceticlastic pathway enzymes are widespread in Bacteria.

Conclusions:

• The two major methane production pathways exhibit significant divergence in their initial enzymatic steps and energy conservation.
• The aceticlastic pathway's prevalence in Bacteria offers insights into broader prokaryotic biology.
• The distinct distribution of these pathways underscores the metabolic diversity within Archaea and Bacteria.