EVIDENCE FOR THE INVOLVEMENT OF MULTIPLE PATHWAYS IN THE BIODEGRADATION OF 1-METHYLNAPHTHALENE AND 2-METHYLNAPHTHALENE BY PSEUDOMONAS-PUTIDA CSVS6

Pseudomonas putida CSV86, a soil bacterium, grows on 1- and 2-methylna phthalene as the sole source of carbon and energy. In order to deduce the pathways for the biodegradation of 1- and 2-methylnaphthalene, met abolites were isolated from the spent medium and purified by thin laye r chromatography. Emphasis has been placed on the structural character isation of isolated intermediates by CC-MS, demonstration of enzyme ac tivities in the cell free extracts and measurement of oxygen uptake by whole cells in the presence of various probable metabolic intermediat es. The data obtained from such a study suggest the possibility of occ urrence of multiple pathways in the degradation of 1- and 2-methylnaph thalene. We propose that, in one of the pathways, the aromatic ring ad jacent to the one bearing the methyl moiety is oxidized leading to the formation of methylsalicylates and methylcatechols. In another pathwa y the methyl side chain is hydroxylated to -CH2-OH which is further co nverted to -CHO and -COOH resulting in the formation of naphthoic acid as the end product. In addition to this, 2-hydroxymethylnaphthalene f ormed by the hydroxylation of the methyl group of 2-methylnaphthalene undergoes aromatic ring hydroxylation. The resultant dihydrodiol is fu rther oxidised by a series of enzyme catalysed reactions to form 4-hyd roxymethyl catechol as the end product of the pathway.