Methane as fuel for anaerobic microorganisms.

Area of Science:

• Microbiology
• Biogeochemistry
• Environmental Science

Background:

• Aerobic methane oxidation by proteobacteria is well-established, utilizing monooxygenase enzymes.
• Anaerobic methane oxidation (AMO) has been recently discovered, but its mechanisms remain unclear.
• AMO is vital for regulating methane release into the atmosphere.

Purpose of the Study:

• To elucidate the mechanisms of anaerobic methane oxidation.
• To identify the microbial players involved in AMO.
• To differentiate AMO pathways from aerobic methane metabolism.

Main Methods:

• Investigated sulfate-dependent AMO catalyzed by methanotrophic archaea and sulfate-reducing delta-proteobacteria.
• Examined methane oxidation coupled to denitrification by novel bacteria.
• Proposed mechanisms involving reversed methanogenesis and glycine-radical enzymes.

Main Results:

• Sulfate-dependent AMO involves methanotrophic archaea and sulfate-reducing bacteria, potentially via reversed methanogenesis.
• Denitrifying bacteria mediate methane oxidation using a novel pathway not involving methyl-coenzyme M reductase.
• The initial step in this novel pathway is likely the formation of 2-methylsuccinate from fumarate and methane.

Conclusions:

• Anaerobic methane oxidation occurs through distinct microbial pathways, differing from aerobic processes.
• Novel enzymes and microbial consortia are responsible for AMO, expanding our understanding of the methane cycle.
• These findings have implications for understanding global carbon cycling and microbial metabolism.