NAD-dependent dehydrogenases enable efficient growth of Paracoccus denitrificans on the PET monomer ethylene glycol.

Ethylene glycol is a monomer of the plastic polyethylene terephthalate (PET) and an environmental pollutant of increasing concern. Although it is generally accepted that bacteria use ethylene glycol as growth substrate, not all involved enzymes are well understood. Here, we show that Paracoccus denitrificans assimilates ethylene glycol solely via NAD-dependent alcohol and aldehyde dehydrogenases. Using comparative proteomics, we identify a gene cluster that is strongly expressed in the presence of ethylene glycol. We report the functional and structural characterization of EtgB and EtgA, key enzymes encoded by this etg gene cluster. We furthermore show that the transcriptional activator EtgR controls expression of the gene cluster. Adaptive laboratory evolution on ethylene glycol results in faster growth, enabled by increased production of EtgB and EtgA. Bioinformatic analysis reveals that the etg gene cluster is widely distributed among bacteria, suggesting a common role of NAD-dependent dehydrogenases in microbial ethylene glycol assimilation.