Artificial electron acceptors decouple archaeal methane oxidation from sulfate reduction

Area of Science:

• Microbial ecology
• Biogeochemistry
• Marine science

Background:

• Methane oxidation with sulfate is a crucial microbial process in the global carbon cycle.
• Marine methane seeps host consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB).
• The symbiotic relationship and metabolic dependencies between ANME and SRB are not well understood.

Purpose of the Study:

• To investigate the metabolic dependencies between ANME and SRB in deep-sea sediments.
• To explore alternative electron transfer mechanisms in anaerobic methane oxidation.
• To test the hypothesis of interspecies extracellular electron transfer as the syntrophic mechanism.

Main Methods:

• Utilized rate measurements to quantify methane oxidation.
• Employed single-cell stable isotope probing to track metabolic activity.
• Introduced soluble artificial oxidants to decouple ANME from SRB.

Main Results:

• ANME demonstrated the ability to oxidize methane using artificial oxidants, independent of SRB.
• High rates of methane oxidation were sustained by ANME even without sulfate.
• Metabolic decoupling of ANME from SRB was achieved using artificial oxidants.

Conclusions:

• ANME can perform methane oxidation with or without their SRB partners when alternative oxidants are available.
• The findings support the hypothesis that interspecies extracellular electron transfer is a primary mechanism for syntrophic methane oxidation.
• This research provides new insights into the uncultured symbiotic partnerships driving the carbon cycle in marine environments.