Bacterial degradation of aromatic compounds via angular dioxygenation

Area of Science:

• Microbiology
• Biochemistry
• Environmental Science

Background:

• Bacterial degradation of aromatic compounds often initiates with dioxygenation.
• Lateral dioxygenation is a common mechanism, forming cis-dihydrodiols.
• Atypical dioxygenation, termed angular dioxygenation, has been identified.

Purpose of the Study:

• To analyze the novel angular dioxygenation pathway in bacterial degradation of aromatic compounds.
• To elucidate the intermediates and products of angular dioxygenation.
• To investigate the genetic basis and evolutionary origins of angular dioxygenase.

Main Methods:

• Analysis of bacterial degradation of fluorene (FN) analogues, dibenzofuran (DF), carbazole (CAR), dibenzothiophene (DBT)-sulfone, dibenzo-p-dioxin (DD), and diphenyl ether (DE).
• Identification of dioxygenation products and intermediates.
• Phylogenetic analysis and substrate specificity comparison of angular dioxygenase.
• Genetic characterization of degradation pathways.

Main Results:

• Angular dioxygenation oxidizes adjacent carbons, differing from lateral dioxygenation.
• Formation of unstable hemiacetal-like intermediates for DF, CAR, DBT-sulfone, DD, and DE, leading to ring cleavage or specific products.
• A stable cis-diol intermediate is formed from 9-fluorenone, leading to further degradation.
• Few bacteria with angular dioxygenase have been reported, with limited pathways characterized at the gene level.

Conclusions:

• Angular dioxygenation represents a novel mechanism for aromatic compound degradation.
• This pathway is linked to the relaxed substrate specificity of the Rieske nonheme iron oxygenase superfamily.
• Degradation pathways involving angular dioxygenation may have arisen from horizontal gene transfer and are not yet evolutionarily mature.