Fig. 7: Conceptual model of dark zone formation integrating taxonomic and functional metagenomic information provided by the present work.

The black arrows represent metabolic pathways identified in this study. The dotted arrows represent the metabolic pathways not identified in this study but expected to occur based on literature information. The blue arrows indicate the link between various benzene-like compounds that can derive from the degradation of BAC, which can then be transformed into carotenoids or L-dopachrome in dark zones. BAC: benzalkonium chloride; BDMA: benzyldimethylamine.