Mechanism of Mercuric Chloride Resistance in Microorganisms: II. NADPH-Dependent Reduction of Mercuric Chloride and Vaporization of Mercury from Mercuric Chloride by a Multiple Drug Resistant Strain of Escherichia coli*

Abstract

The activity to vaporize a ²⁰³Hg compound from ²⁰³HgCl₂ was demonstrated in crude cell-free extracts of a strain of Escherichia coli W2252, which had acquired the multiple drug resistance. NADPH was essential for the vaporization, while NADH had only a slight stimulating effect and NADP⁺ had no effect. The oxidation of NADPH dependent on HgCl₂ was also demonstrated in the crude extracts, but the HgCl₂-dependent NADH oxidation could be demonstrated only when a partially purified enzyme preparation was used. The rate of NADH oxidation was much slower than that of NADPH oxidation. It was concluded that NADPH, and to a lesser extent NADH, act as electron donors for the enzymatic reduction of HgCl₂ and the vaporization occurs after this reduction. This reduction and subsequent vaporization seem to provide a mechanism of resistance to HgCl₂ in E. coli strains having the multiple drug resistance.