Microbial Roles in Dissolved Organic Matter Transformation in Full-Scale Wastewater Treatment Processes Revealed by Reactomics and Comparative Genomics

Understanding
the degradation of dissolved organic matter (DOM)
is vital for optimizing DOM control. However, the microbe-mediated
DOM transformation during wastewater treatment remains poorly characterized.
Here, microbes and DOM along full-scale biotreatment processes were
simultaneously characterized using comparative genomics and high-resolution
mass spectrometry-based reactomics. Biotreatments significantly increased
DOM’s aromaticity and unsaturation due to the overproduced
lignin and polyphenol analogs. DOM was diversified by over five times
in richness, with thousands of nitrogenous and sulfur-containing compounds
generated through microbe-mediated oxidoreduction, functional group
transfer, and C–N and C–S bond formation. Network analysis
demonstrated microbial division of labor in DOM transformation. However,
their roles were determined by their functional traits rather than
taxa. Specifically, network and module hubs exhibited rapid growth
potentials and broad substrate affinities but were deficient in xenobiotics-metabolism-associated
genes. They were mainly correlated to liable DOM consumption and its
transformation to recalcitrant compounds. In contrast, connectors
and peripherals were potential degraders of recalcitrant DOM but slow
in growth. They showed specialized associations with fewer DOM molecules
and probably fed on metabolites of hub microbes. Thus, developing
technologies (e.g., carriers) to selectively enrich peripheral degraders
and consequently decouple the liable and recalcitrant DOM transformation
processes may advance DOM removal.