FIG 4.

Organic nitrogen mineralization and cellular transport are expressed processes in river sediments. Bubble plots indicate the genes that were uniquely assigned to specific MAGs, including those coding for (i) extracellular peptidases and (ii) cellular transporters for organic nitrogen, with expression in metaproteomics (colored circles) and potential (gray circle with colored outline) noted. Unique peptides detected in at least three samples are represented by bubbles and colored by phylum. The table on the right shows putative amino acids cleaved or transported by the respective peptidases (green or gray) or transporters (dark green/black). The shading denotes peptides that are cleaved into amino acids that could be transported, providing linkages between extracellular organic nitrogen transformation and the transport of nitrogen into the cell. No shading (white boxes) indicates an organic nitrogen transporter that recruited peptides but could not be linked to outputs of specific peptidases.