Electron donors utilized by sulfate-reducing bacteria in eutrophic lake sediments.

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Aquatic Ecology

Background:

• Sulfate reduction is a key microbial process in anoxic sediments.
• Understanding substrate utilization by sulfate-reducing bacteria is crucial for biogeochemical cycling.

Purpose of the Study:

• To investigate the role of sulfate reduction in the mineralization of various carbon substrates in eutrophic lake sediments.
• To determine the impact of inhibiting sulfate reduction on overall mineralization rates.

Main Methods:

• Mineralization rates of C-labeled substrates (glucose, lactate, propionate, amino acids, acetate) were measured.
• Sodium molybdate (Na(2)MoO(4)), a sulfate reduction inhibitor, was added at various concentrations.
• Methane production and sulfate reduction were monitored.

Main Results:

• Sodium molybdate effectively inhibited sulfate reduction across all tested concentrations.
• Methane production was inhibited at higher Na(2)MoO(4) concentrations (>20 mM).
• Mineralization of lactate, propionate, and amino acids significantly decreased with Na(2)MoO(4) addition, indicating their reliance on sulfate reduction.

Conclusions:

• Sulfate-reducing bacteria utilize a diverse range of substrates, including lactate, propionate, and amino acids, as electron donors in lake sediments.
• Inhibition of sulfate reduction significantly affects the mineralization of these key organic compounds.
• Sulfate-reducing bacteria are important players in the in situ degradation of organic matter in these sediments.