Alternative Naphthalene Metabolic Pathway Includes Formation of ortho -Phthalic Acid and Cinnamic Acid Derivatives in the Rhodococcus opacus Strain 3D

In this study, we investigated the ability ofRhodococcus opacus strain 3D to utilize naphthalene as a sole carbon and energy source. The characteristic feature of this strain is the inability to grow in the mineral medium supplemented with salicylate (typical intermediate of naphthalene degradation in Gram-negative bacteria). The absence of salicylate hydroxylase activity and salicylate accumulation in the course ofR. opacus 3D cultivation in the mineral medium supplemented with naphthalene indicated existence of an alternative pathway of naphthalene oxidation. At the same time,R. opacus 3D was able to use monoaromatic compounds (salts of gentisic,ortho-phthalic, and 2-hydroxycinnamic acids and coumarin) as growth substrates. Based on the analysis of enzymatic activities, identification of the reaction intermediates, genetic determinants, and growth substrates, we concluded thatR. opacus 3D carries out naphthalene degradation through an alternative pathway via formation of ortho-phthalic acid, which is untypical for pseudomonads. Using mass spectrometry, we showed for the first time that salicylic acid associate formed in trace amounts in the process of naphthalene degradation is not further metabolized and accumulated in the growth medium in a form of a dimer.

Source: Biochemistry (Moscow) - February 29, 2020 Category: Biochemistry Source Type: research