Contribution of Microbial Metabolism to Geogenic Phosphorus Enrichment in Groundwater: Insights from Metagenomic Sequencing and Organic Molecular Characterization

Microbial mediation in the enrichment
of geogenic phosphorus (P)
is often mentioned but rarely explored, especially in P enrichment
processes through the mineralization of dissolved organic matter (DOM)
containing natural P. To bridge the theoretical gap, this study investigated
the mechanisms of P enrichment through microbially mediated mineralization
of natural P-containing DOM by adopting an approach combining comprehensive
field investigation with hydrochemical and molecular biological analyses.
The co-analysis of the dominant microbial community compositions and
genomics revealed that the microbial metabolism pathways involved
in the biodegradation of P-containing DOM were associated with the
enrichment level of dissolved inorganic phosphorus (DIP). Specifically,
dephosphorylation was more pronounced under conditions of limited
DIP, while C–P bond cleavage was the primary metabolic pathway
under sufficient DIP. Co-occurrence network analysis further indicated
that the substrates for DIP enrichment differed between dephosphorylation
and C–P bond cleavage, namely CHONSP1 compounds
in the region of highly unsaturated-low O compounds (AI ≤ 0.5,
H/C < 1.5, and O/C < 0.4) and CHOP1 compounds in
the region of highly unsaturated-high O compounds (AI ≤ 0.5,
H/C < 1.5, and O/C ≥ 0.4), respectively. These findings
provide new insights into geogenic P enrichment in groundwater from
the perspective of microbial metabolism and have potential implications
for the bioremediation of P-contaminated groundwater at different
contamination levels.