Aerobic bacterial methane synthesis.

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Biogenic methane (CH4) production is typically considered an anaerobic process.
• The "methane paradox" describes CH4 supersaturation in oxygenated waters, contradicting this anaerobic view.
• Understanding CH4 sources and sinks is crucial due to its potent greenhouse gas properties.

Purpose of the Study:

• To investigate the microbiological basis of methane production in oxygenated environments.
• To identify organisms and genes involved in aerobic methane synthesis.
• To elucidate the biochemical pathway of methylamine conversion to methane.

Main Methods:

• Isolation and characterization of a CH4-producing bacterium from Yellowstone Lake.
• Identification and cloning of the key gene responsible for the observed activity.
• Heterologous expression of the gene in Escherichia coli and characterization of the purified enzyme.

Main Results:

• An Acidovorax sp. was isolated and shown to convert methylamine to CH4.
• A gene encoding pyridoxylamine phosphate-dependent aspartate aminotransferase was identified as critical for this process.
• The methylamine-to-CH4 conversion activity was successfully transferred to E. coli and observed with the purified enzyme.

Conclusions:

• A previously unrecognized aerobic pathway for methane synthesis from methylamine has been identified.
• This oxygen-insensitive process suggests widespread aerobic methane production in the environment.
• The findings necessitate re-evaluation of methane cycling models to include aerobic pathways.