Cable bacteria regulate sedimentary phosphorus release in freshwater sediments

Area of Science:

• Environmental microbiology
• Geochemistry
• Biogeochemical cycling

Background:

• Electrogenic sulfur oxidation (e-SOx) regulates phosphorus release in marine and brackish sediments by forming metal oxide layers.
• Cable bacteria, capable of e-SOx, are found in freshwater systems where their role in phosphorus cycling is less understood.
• Limited sulfide production in freshwater may affect metal oxide layer dissolution and phosphorus release.

Purpose of the Study:

• To investigate the impact of cable bacteria on iron, manganese, and phosphorus cycling in freshwater sediments.
• To determine if cable bacteria influence phosphorus availability in eutrophic freshwater streams.

Main Methods:

• Incubation of freshwater river sediments.
• High-resolution depth profiling of pH, O2, and sulfide.
• Fluorescence in situ hybridization (FISH) and high-throughput gene sequencing.

Main Results:

• Cable bacteria enrichment correlated with e-SOx activity and sediment acidification.
• Acidification led to iron and manganese mineral dissolution and porewater release.
• Formation of a metal oxide layer at the sediment surface trapped phosphorus, reducing its availability.

Conclusions:

• Cable bacteria play a significant role in regulating phosphorus cycling in freshwater sediments.
• The metal oxide layer formed by cable bacteria activity effectively traps phosphorus.
• Cable bacteria may act as a natural mechanism to mitigate eutrophication in freshwater systems.