Characterization of a novel aromatic substrate-processing microcompartment in Actinobacteria.

Area of Science:

• Microbiology and Molecular Biology
• Biochemistry and Metabolic Pathways

Background:

• Bacterial microcompartments (BMCs) are proteinaceous organelles that confer environmental advantages.
• BMCs are formed by genetic loci encoding shell proteins and enzymatic cores, enabling discovery of novel functions.
• ARO loci, exclusive to Actinobacteria, contain genes for shell proteins and aromatic compound degradation.

Purpose of the Study:

• To detail the distribution, composition, and phylogenetic characteristics of the ARO BMC locus in Actinobacteria.
• To conduct phylogenetic, structural, and functional analyses of key enzymes in the ARO pathway.
• To characterize the ARO BMC's role in degrading aromatic compounds, specifically 2-aminophenol and catechol.

Main Methods:

• Genomic analysis to determine ARO locus variations across bacterial orders.
• Phylogenetic, structural, and functional analyses of 2-aminophenol dioxygenase and semialdehyde dehydrogenase.
• In vitro enzymatic assays to assess substrate cleavage by the dioxygenase and dehydrogenase.

Main Results:

• Discovered a unique ARO BMC locus in Actinobacteria, containing genes for 2-aminophenol meta-cleavage pathway and BMC shell proteins.
• Identified variations in ARO locus complexity, with some encoding complete degradation pathways and others partial.
• Demonstrated in vitro cleavage of 2-aminophenol and catechol by the characterized enzymes, confirming their role in metabolizing toxic intermediates.

Conclusions:

• The ARO BMC locus represents a novel system for aromatic compound degradation in Actinobacteria.
• Two subtypes of ARO BMCs are proposed, potentially degrading either 2-aminophenol or catechol.
• The characterized enzymes facilitate the breakdown of unstable aromatic intermediates, highlighting BMCs' metabolic versatility.