FIG. 1.

Effect of HMN on the biotransformation of naphthalene by Pseudomonas sp. strain 9816/11 (a) and S. yanoikuyae B8/36 (b) and of phenanthrene by Pseudomonas sp. strain 9816/11 (c) and S. yanoikuyae B8/36 (d). HMN was added at a ratio of 5 ml per 100 ml of cell suspension (○). Control flasks (●) had no HMN added. Strains were grown using published methods (induction being required for expression of dioxygenase enzymes for both biotransformation and enzyme assay experiments) (25). For all biotransformation experiments, cells were resuspended in 0.1 M potassium phosphate buffer (pH 7.5; A₆₀₀ = 1.1). Sodium succinate (31 mM) was used as a cosubstrate, and (unless otherwise stated) PAH substrates were added at a concentration of 0.9 g liter⁻¹. All biotransformations were conducted in triplicate; data points show the mean concentrations of cis-dihydrodiol metabolites in the aqueous phase. HPLC analysis using an octyldecyl silane 15-cm reverse-phase column (50 to 70% methanol-water gradient over 30 min, 0.5 ml min⁻¹ flow rate) of phenanthrene metabolites was performed at 260 nm, and analysis of naphthalene metabolites was performed at 265 nm.