Escherichia coli 6-phosphogluconate dehydrogenase aids in tellurite resistance by reducing the toxicant in a NADPH-dependent manner

• Published in: Microbiological research 2015-08, Vol.177, p.22-27
• Main Authors: Sandoval, J.M., Arenas, F.A., García, J.A., Díaz-Vásquez, W.A., Valdivia-González, M., Sabotier, M., Vásquez, C.C.
• Format: Article
• Language: English
• Subjects: Drug Resistance, Bacterial; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - enzymology; Escherichia coli - metabolism; G6PDH; Gnd protein; Inactivation, Metabolic; NADP - metabolism; NADPH; Oxidation-Reduction; Phosphogluconate Dehydrogenase - metabolism; Tellurite reduction; Tellurium - metabolism; Tellurium - toxicity
• ISSN: 0944-5013; 1618-0623
• DOI: 10.1016/j.micres.2015.05.002

Exposure to the tellurium oxyanion tellurite (TeO32−) results in the establishment of an oxidative stress status in most microorganisms. Usually, bacteria growing in the presence of the toxicant turn black because of the reduction of tellurite (Te4+) to the less-toxic elemental tellurium (Te0). In vitro, at least part of tellurite reduction occurs enzymatically in a nicotinamide dinucleotide-dependent reaction. In this work, we show that TeO32− reduction by crude extracts of Escherichia coli overexpressing the zwf gene (encoding glucose-6-phosphate dehydrogenase) takes place preferentially in the presence of NADPH instead of NADH. The enzyme responsible for toxicant reduction was identified as 6-phosphogluconate dehydrogenase (Gnd). The gnd gene showed a subtle induction at short times after toxicant exposure while strains lacking gnd were more susceptible to the toxicant. These results suggest that both NADPH-generating enzymes from the pentose phosphate shunt may be involved in tellurite detoxification and resistance in E. coli.