The presence of benzene ring activating CoA ligases for aromatics degradation in the ANaerobic MEthanotrophic (ANME) archaea

Petroleum-source and black carbon-source aromatic compounds are present in the cold seep environments, where ANaerobic MEthanotrophic (ANME) archaea as the dominant microbial community mediates the anaerobic oxidation of methane to produce inorganic and organic carbon. Here, by predicting the aromatics catabolic pathways in ANME metagenome-assembled genomes, we provide genomic and biochemical evidences that ANME have the potential of metabolizing aromatics via the strategy of CoA activation of the benzene ring using phenylacetic acid and benzoate as the substrates. Two ring-activating enzymes phenylacetate-CoA ligase (PaaK(ANME)) and benzoate-CoA ligase (BadA(ANME)) are able to convert phenylacetate to phenylacetyl-CoA and benzoate to benzoyl-CoA in vitro, respectively. They are mesophilic, alkali resistance, and with broad substrate spectra showing different affinity with various substrates. An exploration of the relative gene abundance in ANME genomes and cold seep environments indicates that about 50% of ANME genomes contain PCL genes, and various bacteria and archaea contain PCL and BCL genes. The results provide evidences for the capability of heterotrophic metabolism of aromatic compounds by ANME. This has not only enhanced our understanding of the nutrient range of ANME but also helped to explore the additional ecological and biogeochemical significance of this ubiquitous sedimentary archaea in the carbon flow in the cold seep environments. IMPORTANCE: ANaerobic MEthanotrophic (ANME) archaea is the dominant microbial community mediating the anaerobic oxidation of methane in the cold seep environments, where aromatic compounds are present. Then it is hypothesized that ANME may be involved in the metabolism of aromatics. Here, we provide genomic and biochemical evidences for the heterotrophic metabolism of aromatic compounds by ANME, enhancing our understanding of their nutrient range and also shedding light on the ecological and biogeochemical significance of these ubiquitous sedimentary archaea in carbon flow within cold seep environments. Overall, this study offers valuable insights into the metabolic capabilities of ANME and their potential contributions to the global carbon cycle.