Microbially driven methane and sulfur cycling processes and coupling mechanisms in mangrove sediments

Area of Science:

• Environmental Microbiology
• Biogeochemical Cycles
• Marine Science

Background:

• Mangrove sediments are significant sources of biogenic methane (CH4), a potent greenhouse gas.
• These environments harbor complex microbial communities involved in carbon and sulfur cycling.
• Understanding methane and sulfur cycling coupling is crucial for climate change research.

Purpose of the Study:

• To investigate the microbial communities and environmental factors influencing methane and sulfur cycling in mangrove sediments.
• To elucidate the coupling mechanisms between methane and sulfur cycling processes.
• To provide insights into mitigating global warming through better understanding of these cycles.

Main Methods:

• Metagenome sequencing of mangrove sediment cores.
• Analysis of microbial community structure, including methanogens, anaerobic methanotrophic archaea (ANME), sulfate-reducing bacteria (SRB), and sulfur-oxidizing bacteria.
• Metagenome-assembled genome (MAG) analysis to identify metabolic pathways and interspecies interactions.
• Correlation network analysis to assess microbial interactions and environmental factor influences.

Main Results:

• Methanomicrobiales and Methanophagales were dominant methanogens; Methanospirareceae represented ANME; Desulfobacteraceae and Desulfobulbaceae were abundant SRB; Ectothiorhodospiraceae, Chromatiaceae, and Comamonadaceae were dominant S-oxidizers.
• Positive interactions were observed among methanogens, ANME, and SRB.
• Interspecies hydrogen transfer and extracellular electron exchange via conductive pili, flagella, and cytochromes were identified as potential coupling mechanisms.
• ANME can form consortia with SRB via intermediate metabolites or direct interspecies electron transfer.
• Methanogen and ANME MAGs revealed pathways for sulfur metabolism, including thiosulfate oxidation, sulfate reduction, and sulfur disproportionation.
• Sulfate, total sulfur, moisture, and salinity significantly impacted microbial community structure and cycling gene families.

Conclusions:

• This research provides novel insights into the intricate coupling mechanisms of methane and sulfur cycling in mangrove sediments.
• The identified microbial interactions and metabolic pathways are key to understanding greenhouse gas dynamics in these ecosystems.
• The findings have significant implications for developing strategies to mitigate global warming.