Evidence of two metabolic pathways for degradation of 2-methylphenanthreneby Sphingomonas sp strain (2MPII)

A pure bacterial strain of Sphingomonas sp. DSM 11572 (named 2MPII) has bee n isolated from a Mediterranean coastal sediment. This strain is able to us e 2-methylphenanthrene (2-MP) as a growth substrate. In order to understand the degradation processes and their selectivity, we have elucidated the me tabolic pathways of 2-MP degradation. In this respect, in this paper, we re port the identification of several metabolites resulting from the oxidation of 2-MP by the Sphingomonas sp. Metabolites of 2-MP, identified by gas chr omatography coupled to mass spectrometry in culture media, belong to two di stinct metabolic pathways. The first pathway involves, in the first step, t he double hydroxylation of an aromatic ring catalyzed by a di-oxygenase. Th is pathway generates before the opening of the aromatic ring. The exact dou ble hydroxylation positions have not been totally elucidated. The second pa thway is initiated by the hydroxylation of the methyl side chain by a mono- oxygenase. It leads, by the oxidation of the methyl group, to the formation of alcohol, aldehyde, and carboxylic acid.