Riverine plastic litter restructures microbial vitamin B12 metabolism and generates functional heterogeneity

Riverine plastic litter significantly alters microbial vitamin B12 metabolism, creating functional diversity, according to a study characterizing plastisphere and water-column communities along the River Rhine. The researchers analyzed ATR-FTIR polymer characterization, 16S/18S rRNA amplicon profiles, and 120 metagenome-assembled genomes from 14 stations.

Plastisphere communities exhibited distinct taxonomic profiles from water communities (PERMANOVA R = 0.258, p = 0.0001). Although the functional centroid remained similar (R = 0.245, p = 0.125), functional composition across sites was notably more varied (permutest p = 0.0047). The core B12 biosynthetic pathway, aerobic corrin ring synthesis, was among the most differentiated functions and enriched on plastic at all paired stations (Wilcoxon exact test, W = 3, p = 0.004079).

This finding correlated with a diatom-dominated eukaryotic plastisphere community; diatoms cannot synthesize B12 and rely on bacterial provision. The presence of plastisphere communities was less tightly linked to the river's dissolved nutrient gradient compared to water communities (envfit R = 0.64 vs. 0.82). These results demonstrate that riverine plastic litter actively reshapes specific metabolic abilities of its inhabitants, with vitamin B12 metabolism serving as a prime example.