Elevated nitrate simplifies microbial community compositions and interactions in sulfide-rich river sediments.

Area of Science:

• Environmental Microbiology
• Aquatic Ecology
• Biogeochemistry

Background:

• Nitrate pollution poses a global health risk, with river sediments acting as hotspots for denitrification.
• Sulfide-rich sediments harbor complex anaerobic microbial communities, but their response to nitrate surges is poorly understood.

Purpose of the Study:

• To investigate the ecological effects of a nitrate surge on microbial dynamics in sulfide-rich river sediments.
• To identify key microbial players and functional shifts in response to nitrate pollution.

Main Methods:

• Simulated a nitrate surge in sulfide-rich river sediment over one month.
• Monitored microbial community responses and environmental parameters.
• Utilized microbial community analysis and network analysis.

Main Results:

• Elevated nitrate induced functional convergence (denitrification, sulfide oxidation) and taxonomic convergence (Proteobacteria).
• Significant loss of biodiversity, community stability, and other functions observed.
• Chemolithotrophic denitrifiers Thiobacillus and Luteimonas were enriched; Thiobacillus thiophilus dominated due to dual nitrate reduction and sulfide oxidation capabilities.
• Keystone taxa were identified as native auxotrophs, with nitrate perturbation disrupting cross-feeding interactions.

Conclusions:

• Nitrate pollution simplifies microbial interactions and functions in sulfide-rich sediments.
• Thiobacillus thiophilus demonstrates a key role in adapting to nitrate-rich, sulfide-containing environments.
• Understanding these microbial responses is crucial for managing nitrate-polluted aquatic systems.