Novel phosphorylation of aldrin-trans-diol by dieldrin-degrading fungus Mucor racemosus strain DDF

•Mucor racemosus strain DDF degraded the dieldrin metabolite, aldrin-trans-diol.•The plausible metabolites, aldrin-trans-diol sulfonates and phosphonate, were synthesized.•The two metabolites were confirmed as aldrin-trans-diol exo- and endo-phosphates.•This is the first reported example of phosphate conjugation in microorganisms.

Dieldrin is one of the most persistent organic pollutants, and its oxidative degradation pathways by aerobic microorganisms to 6,7-trans-dihydroxydihydroaldrin (otherwise known as aldrin-trans-diol) and 9-hydroxydieldrin are well documented. The dieldrin-degrading fungus, Mucor racemosus strain DDF, can decrease dieldrin levels with simultaneous production of a small amount of aldrin-trans-diol. A reduction in the levels of aldrin-trans-diol by strain DDF has also been observed. Based on these results, it has been suggested that strain DDF transforms dieldrin to more polar compounds via aldrin-trans-diol. We have conducted a study to identify the metabolites arising from aldrin-trans-diol. The results showed that strain DDF gave reduced levels of aldrin-trans-diol and also produced unknown metabolites. Ultra performance liquid chromatography-electrospray ionization-mass spectroscopy (UPLC-ESI-MS) analysis indicated the metabolites to be either sulfated- or phosphorylated- derivatives of aldrin-trans-diol, but with the metabolites retaining six chlorine atoms. Therefore, the candidate derivatives were synthesized and the retention times of the natural metabolite and the synthetic phosphate were compared. As a result of a co-injection experiment, the metabolites were determined to be aldrin-trans-diol exo- and endo-phosphates. These results were also supported by high-resolution-fast atom bombardment-mass spectrometry (HR-FAB-MS) of the natural metabolite (Δ = 0.63 ppm). Phosphorylation of aldrin-trans-diol is the first reported example of phosphate conjugation in microorganisms.