Trace methane oxidation studied in several Euryarchaeota under diverse conditions

Area of Science:

• Microbiology
• Biogeochemistry
• Environmental Science

Background:

• Methanogens produce methane, but the extent of methane oxidation by these microbes is not fully understood.
• Investigating methane oxidation in methanogens is crucial for understanding carbon cycling and microbial metabolism.

Purpose of the Study:

• To quantify trace methane oxidation in various methanogen species and Archaeoglobus under different growth conditions.
• To explore potential electron acceptors and cofactors involved in methane oxidation by methanogens.

Main Methods:

• Utilized (13)C-labeled methane to trace and quantify methane oxidation during growth of selected methanogens and Archaeoglobus species.
• Grew microbes on different substrates (H(2)/CO(2), trimethylamine, methanol) and tested the effect of electron acceptors (O(2), NO(3)(-), SO(4)(2-), SO(3)(2-)) and cofactors (FAD, NAD(+)).

Main Results:

• Methane oxidation rates varied significantly among methanogen species and substrates, with Methanosarcina acetivorans showing higher oxidation on trimethylamine than methanol.
• Methanobacterium thermoautotrophicum and Methanosarcina barkeri exhibited different methane oxidation extents when grown on H(2) and CO(2).
• Archaeoglobus species showed negligible methane oxidation, suggesting methyl-coenzyme M reductase is essential for this process.

Conclusions:

• Trace methane oxidation during methanogenesis is species- and substrate-dependent and likely independent of common electron acceptors and H(2) concentration.
• The absence of methane oxidation in Archaeoglobus suggests that methyl-coenzyme M reductase is a key enzyme for anaerobic methane oxidation.
• Findings contribute to understanding the microbial methane cycle and the metabolic capabilities of methanogens and related archaea.