Biodiversity and nitrogen metabolism in the plastisphere impacted by urban nitrogen loading from a coastal mega-city

The plastisphere, recognized for vast biomass and critical role in nitrogen cycling, is becoming a pertinent component of marine ecosystems. The relationship between plastisphere and increased nitrogen inputs from urban wastewater in coastal zones remains poorly understood. Through metagenomics, metatranscriptomics and metabolomics, this research sought to elucidate the plastisphere's reaction to elevated nitrogen loading and pinpoint key microbial resources that can be harnessed. Although the archaeal community composition within the plastisphere remains largely unchanged by nitrogen loading, bacterial diversity experiences a substantial boost, which is inversely correlated with fungal diversity. Furthermore, such conditions are associated with reduced intricate microbial interactions. Moreover, the plastisphere subjected to nitrogen loading shows an enrichment of genera and genes implicated in ammonium assimilation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Metabolomics analysis highlighted the plastisphere's accumulation of L-glutathione oxidized (GSSG) in response to nitrogen loading. The research further highlighted a quartet of microbial phyla-Actinomycetota, Bacteroidota, Cyanobacteriota, and Pseudomonadota-that not only thrive but also constitute pivotal microbial resources within the plastisphere when confronted with strong nitrogen loading. In essence, this investigation illuminates the plastisphere's biodiversity dynamics and nitrogen metabolic adjustments during augmented nitrogen loading and offers novel perspectives on taking advantage of the plastisphere's untapped microbial potential.