Electric coupling between distant nitrate reduction and sulfide oxidation in marine sediment
Ugo Marzocchi1, Daniela Trojan1, Steffen Larsen2
1Section for Microbiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
The ISME Journal
|March 1, 2014
Summary
Cable bacteria in marine sediment can now use nitrate or nitrite as electron acceptors. This couples distant sulfide oxidation to nitrate reduction, revealing a new biogeochemical process.
Area of Science:
- Microbiology
- Geochemistry
- Environmental Science
Background:
- Filamentous Desulfobulbaceae (cable bacteria) conduct electricity over long distances in marine sediments.
- They link surface oxygen reduction to deep sulfide oxidation.
- Their capacity to utilize alternative electron acceptors was previously unknown.
Purpose of the Study:
- To investigate if cable bacteria can use nitrate or nitrite as electron acceptors.
- To understand the implications for marine biogeochemical cycling.
Main Methods:
- Incubation of sulfidic marine sediment with nitrate-amended anoxic seawater.
- Monitoring for spatial separation of redox processes and pH changes.
- Microscopic identification of Desulfobulbaceae.
Main Results:
- A 4-6 mm zone formed, separating sulfide oxidation from nitrate reduction.
- pH signatures indicated proton consumption (nitrate reduction) and production (sulfide oxidation).
- Filamentous Desulfobulbaceae were detected in nitrate-amended incubations.
Conclusions:
- Cable bacteria can utilize nitrate/nitrite as electron acceptors, coupling distant sulfide oxidation.
- This represents a novel mechanism in nitrogen and sulfur cycling.
- Further research is needed to quantify the impact on elemental cycles.
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