Transformation of Methoxylated Aromatic Compounds by Anaerobic Microorganisms

Methoxylated aromatic compounds (MAC) are widely distributed in various habitats and are components of lignin, the second most abundant biopolymer on Earth. This review summarizes the results on microbiology, ecology, and biochemistry of anaerobic MAC catabolism in bacteria and archaea. We analyzed the genomes of 46 prokaryotes anaerobically degrading MAC for the presence of O-demethylase, CO-dehydrogenase/acetyl-CoA synthase, and benzoyl-CoA reductase genes, which determine the possibility of methoxydotrophic growth. It was found that facultative anaerobes of the phylum Pseudomonadota do not have any known genetic determinants of anaerobic O-demethylase reaction as well as of aromatic ring reduction. Thus, the MAC transformation by anaerobic microorganisms can be carried out by diverse biochemical mechanisms and probably plays a more significant role in the global carbon cycle than previously supposed.