The genetic organization of Mbn-producing operons. Genomic regions containing all identified Mbn operons are depicted. Operons are grouped into five families on the basis of operon content, MbnB conservation, and MbnA sequence. All operons contain MbnA (black) and MbnB (orange) and at least one transport protein, a MATE efflux pump (purple), a TonB-dependent transporter (blue) or both. Most operons contain additional biosynthesis-related genes, including MbnC (green), aminotransferases (MbnN, brown) or sulfotransferases (MbnS, dark purple). Additional genes may be related to regulation (MbnR, yellow and MbnI, red) or may play an unknown role in copper homeostasis (MbnP, gold and MbnH, dark blue) Genetic mobility elements of several varieties (light teal) are common in the vicinity of these operons. Metagenomic samples corresponding to unidentified or provisionally identified species are marked (†).