FIGURE 3 

Categorisation of the three partially overlapping sets of metabolic pathways that form the global biodegradation network. The sets of chemicals and their metabolic products were defined according to their final environmental sinks: (i) NBs, chemicals that cannot be degraded (nonbiodegradable) and metabolic precursors of molecules that cannot be degraded; (ii) CMs, chemicals that belong to the central metabolism and precursors that are biologically processed to central metabolites; (iii) CDs, molecules that are directly channelled to production of CO₂; (iv) CMCDs, the sum of CMs and CDs. The general trend of these types of compounds towards recalcitrance or biodegradation is sketched on top.