Zero-valent sulphur is a key intermediate in marine methane oxidation

Area of Science:

• Marine microbial ecology
• Biogeochemical cycles
• Microbial metabolism

Background:

• Marine sediments are a major source of methane, a potent greenhouse gas.
• Anaerobic oxidation of methane (AOM) coupled to sulfate reduction is the primary control on methane emissions.
• Current understanding posits AOM is mediated by a syntrophic partnership between methanotrophic archaea (ANME) and sulfate-reducing Deltaproteobacteria.

Purpose of the Study:

• To elucidate the mechanism of sulfate-coupled anaerobic oxidation of methane (AOM).
• To investigate the roles of methanotrophic archaea (ANME) and Deltaproteobacteria in AOM.
• To explore novel microbial pathways in sulfur transformation.

Main Methods:

• Investigated microbial consortia from marine sediments.
• Analyzed the metabolic pathways involved in anaerobic oxidation of methane (AOM).
• Identified zero-valent sulfur compounds (S(0)) as intermediates in AOM.

Main Results:

• Methanotrophic archaea (ANME) perform dissimilatory sulfate reduction, producing zero-valent sulfur compounds (S(0)).
• AOM can occur independently of Deltaproteobacteria, challenging the obligate syntrophic model.
• Associated Deltaproteobacteria disproportionate the produced S(0) into disulfide.

Conclusions:

• The discovery of a novel sulfate reduction pathway in ANME expands known microbial sulfur transformations.
• AOM may not require syntrophy, with ANME potentially acting alone.
• These findings significantly advance our understanding of marine carbon and sulfur biogeochemical cycles.