Manganese-oxidizing bacteria mediate the degradation of 17α-ethinylestradiol.
Bottom Line: The presence of manganese (II) was found to be essential for the degradation of EE2 by Leptothrix discophora, Pseudomonas putida MB1, P. putida MB6 and P. putida MB29.Mn(2+)-dependent degradation of EE2 was found to be a slow process, which requires multi-fold excess of Mn(2+) and occurs in the late stationary phase of growth, implying a chemical process taking place.EE2-derived degradation products were shown to no longer exhibit undesirable estrogenic activity.
Affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Ghent, Belgium.Show MeSH
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Mentions: The initial concentrations of Mn2+ used in this study are known from the earlier studies to induce Mn oxidation, but were by far represented in excess compared with 0.5 µM EE2. In order to establish a lower limit of Mn2+ which starts to catalyse degradation of EE2, LMG 2322 was grown with 0.5 µM of EE2 and 1, 10 and 50 µM Mn2+. Degradation of EE2 is dependent on the amount of Mn2+ present in the medium and that multi‐fold excess of Mn2+ was required (Fig. 1). Most of EE2 was degraded in the late stationary phase and thus was not linked to the growth of the bacteria (Fig. 1). Moreover, the degradation of EE2 occurred in time after Mn oxidation: for the culture with 50 µM of Mn2+ most of EE2 was degraded in the period between 24 and 36 h, whereas most of Mn2+ was oxidized earlier, in the period between 18 and 24 h (Fig. 1). This delay is likely to be linked to the primary accumulation of significant amounts of biogenic Mn oxides, which then start to react with EE2. Thus, degradation of EE2 is a slow chemical process that is not dependent on the presence of viable bacterial cells, but rather on the amount of biogenic Mn oxides produced. Influence of microbial activity on Mn‐dependent degradation of EE2 was tested by addition of sodium azide, a known inhibitor of electron transport‐linked oxidation. Pseudomonas putida was grown in presence of 100 µM of MnCl2 until orange coloured Mn oxides were visible and EE2 and sodium azide at a concentration of 1 mM were added. A culture without sodium azide was used as a control. Addition of sodium azide still allowed 80% degradation of EE2, whereas without azide complete degradation of EE2 occured. We suspect that the 20% inhibition caused by azide could be linked to inability of the azide‐treated cultures to regenerate Mn oxides.
Affiliation: Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Ghent, Belgium.