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Substrates for sulfate reduction and methane production in intertidal sediments.
1Department of Microbiology, Montana State University, Bozeman, Montana 59717.
Applied and Environmental Microbiology
|January 1, 1983
Summary
Methane production in marine sediments is slow until sulfate is depleted. Methylamine, not acetate or other compounds, stimulates methane production in sulfate-rich environments, suggesting novel methane sources.
Area of Science:
- Microbial ecology
- Biogeochemical cycles
Background:
- Methane-producing bacteria (methanogens) and sulfate-reducing bacteria (SRB) are key players in anaerobic sediment environments.
- Understanding their substrate utilization is crucial for comprehending carbon cycling in intertidal zones.
Purpose of the Study:
- To investigate the activity and potential substrates for methanogens and SRB in various intertidal sediments.
- To determine the relationship between sulfate reduction and methane production rates.
- To identify novel substrates for methanogenesis in sulfate-rich conditions.
Main Methods:
- Incubation of marsh, estuary, and beach intertidal sediments.
- Measurement of methane production and sulfate reduction rates.
- Addition of potential substrates (methylamine, acetate, hydrogen, methionine) and inhibitors (molybdate, fluoracetate) to assess microbial activity.
- Use of radiolabeled compounds ([C]methylamine, [methyl-C]methionine, [2-C]acetate) to trace metabolic pathways.
Main Results:
- Sulfate reduction rates were significantly higher (100- to 1,000-fold) than methane production rates in all tested sediments.
- Methane production sharply increased only after sulfate depletion.
- Methylamine addition stimulated methanogenesis in the presence of sulfate, with rapid conversion to methane and CO(2).
- Acetate, hydrogen, or methionine did not stimulate methanogenesis; radiolabeled acetate and methionine were converted to CO(2), not methane.
- Inhibitor studies indicated acetate is a major electron donor for sulfate reduction, and molybdate inhibited acetate metabolism.
Conclusions:
- Acetate serves as a primary electron donor for sulfate reduction in marine sediments.
- In sulfate-rich environments, methane production is limited, but novel substrates like methylamine can support methanogenesis.
- The findings highlight the complex interplay between sulfate reduction and methanogenesis and identify methylamine as a potential methane precursor in marine sediments.