Single-Cell Profiling Reveals Hidden Drivers of Sediment Phosphorus Release

Area of Science:

• Environmental Microbiology
• Aquatic Ecology
• Biogeochemistry

Background:

• External phosphorus inputs are decreasing, but internal phosphorus release from sediments fuels eutrophication and algal blooms.
• Studying phosphorus-solubilizing bacteria (PSB) in situ is challenging due to cultivation biases and disconnects between genetic profiles and cell function.
• Understanding the interplay between PSB activity and genetic adaptation in sediments is crucial for managing internal phosphorus release.

Purpose of the Study:

• To quantify in situ phosphorus-solubilizing activities of PSB across different trophic states (eutrophic, mesotrophic, oligotrophic).
• To investigate the phenotypic activity and adaptive genetic strategies of PSB in heterogeneous sedimentary environments.
• To elucidate the mechanisms of endogenous phosphorus release and inform lake management strategies.

Main Methods:

• Single-cell Raman spectroscopy combined with deuterium oxide labeling (Raman-D2O) to measure in situ metabolic activity.
• Raman-activated cell sorting followed by metagenomic sequencing to link microbial function with genetic makeup.
• Analysis of phosphorus speciation and release fluxes at the sediment-water interface.

Main Results:

• Distinct in situ phosphorus-solubilizing activities of PSB were quantified across eutrophic, mesotrophic, and oligotrophic sediments.
• Inorganic PSB were dominant and most active in eutrophic sediments, correlating with phosphorus release.
• Organic PSB prevailed in oligotrophic sediments, and low-abundance taxa like Bacillus and Acinetobacter disproportionately drove phosphorus mobilization.
• PSB from eutrophic sediments showed enrichment in phosphatase and organic acid hydrolysis genes, while oligotrophic PSB favored high-affinity transporters and polyphosphate storage genes.

Conclusions:

• Nutrient regimes significantly shape the metabolic traits and adaptive genetic strategies of PSB.
• Mechanistic insights into microbial phosphorus dynamics are advanced, highlighting the role of PSB in endogenous phosphorus release.
• Findings provide a theoretical basis for optimizing lake management to mitigate eutrophication risks driven by internal phosphorus loading.