Fig. 4. Plots showing the distribution of N cycling mechanisms across MAGs, including DNRA and denitrification pathway fragmentation.

A Number of MAGs with genes or genes expressed per pathway, with indicative genes required for each step from nitrate to ammonia or N₂ to denote complete DNRA or denitrification potential, respectively. B Number of MAGs with marker genes and marker genes overall for key N cycling processes: two steps for nitrification (purple), four steps for denitrification (dark green), DNRA (light green), and anammox (red). C Number of MAGs with at least one copy of each marker gene or marker gene expressed across groundwater samples and sites (A–D).